Time Machine is a key selling point for Leopard and the Mac. It is more complete, and yet simpler, than the built-in backup feature in Vista Home Premium, the most popular home version of Windows.

But Time Machine has a major drawback: It works much better on desktop Macs than on laptop models. That’s because it’s primarily designed to operate with backup hard drives you connect directly to the computer. And it’s a pain to plug a backup drive into a laptop, which can move around the house. While Time Machine will work with a remote hard disk under certain circumstances, that option requires a second Mac running Leopard, a costly condition.

Now, Apple (AAPL) has attempted to fix the problem with an unusual new companion product called Time Capsule. This is a $299 stand-alone networked gadget that packs both a giant hard disk and a speedy Wi-Fi wireless router into one slender case. It just plugs into your existing home network, and any laptop within wireless range can connect to it. It can back up multiple computers.

Time Capsule is designed to seamlessly work with Leopard’s Time Machine. But it can also be used as a wireless Internet connection, and/or a remote hard drive, for manually storing and retrieving files by Windows PCs running either Vista or Windows XP, or by Macs running Apple’s older Tiger operating system. And you can also use it with certain other backup programs, such as the ones built into Windows XP or Tiger.

In my tests over the past week, Time Capsule worked well in all of these scenarios. However, Time Capsule isn’t meant to do as many different tasks as some other networked drives.

Apple stresses that Time Capsule is a limited, targeted device meant primarily for backup — especially with Time Machine — and as a wireless base station. Unlike some other networked storage devices, like Hewlett-Packard’s MediaSmart home server, Time Capsule doesn’t allow users to simultaneously stream music or videos to multiple PCs, to easily access its contents via the Web or to stream videos to TV sets.

The $299 Time Capsule model comes with a 500 gigabyte hard disk inside, and there’s also a $499 model with hard disk that can hold one terabyte of data, or roughly 1,000 gigabytes. Both models use the same “n” class of Wi-Fi, the fastest version with the longest range. Both also work with computers equipped with the older “g” and “b” versions of Wi-Fi.

You can buy networked hard disks in these sizes for less money and simply use them with your existing Wi-Fi router. However, Time Machine won’t work with them, according to Apple. The company says the only standalone networked hard disk Time Machine can use is Time Capsule.

In my tests, Time Capsule performed perfectly with Time Machine. It also was easily recognized by several of my Windows machines running Vista and Windows XP. On all of these machines, I was able to speedily access the Internet via Time Capsule. Time Capsule can be set up to either replace or supplement your existing Wi-Fi router.

All the machines, even the Windows ones, also could recognize the Time Capsule as a remote hard disk, and save files to it and retrieve files from it. For instance, I manually copied a song, a photo and a Word document from a Mac laptop running Leopard onto the Time Capsule. On a Dell running Vista, I then opened the Time Capsule and launched that same Word document in the Windows version of Word, opened the photo in Vista’s Photo Gallery program, and played the song in Windows Media Player. This same process worked in reverse.

Apple doesn’t guarantee that Time Capsule will work with all backup programs. But it says it will work with the backup software built into Tiger and will likely work with some other backup software.

In my tests, the built-in backup program in Windows XP Pro worked fine with Time Capsule. But the built-in backup program in Vista failed. Microsoft said the problem I encountered was due to a new Vista security feature for backups that foils some remote hard disks, not just Apple’s.

Setting up Time Capsule was easy, using a step-by-step utility program that Apple supplies in both Mac and Windows versions. The device has a USB port that can be used to add either an additional hard disk or a networked printer. And it can be connected to a network via a wired connection if you don’t want to use its wireless functionality.

If you use Time Machine on a Mac laptop, then Time Capsule’s $299 price is money well spent. If you don’t, there are cheaper or more versatile solutions to the backup problem.

• Email me at mossberg@wsj.com. Find all my columns and videos online, free, at the new All Things Digital Web site, http://walt.allthingsd.com.

There are several reasons for this, including the security problems in the dominant Windows platform from Microsoft; spillover from Apple’s blistering success with its iPod music players; the fact that Macs can now run Windows programs; and Apple’s highly successful chain of company-owned retail stores.

But another key factor has been the Mac operating system, called OS X, which came out in 2001. It has proved to be as powerful and versatile for mainstream consumers as Windows, yet easier to use and more secure. And Apple has upgraded OS X far more rapidly than Microsoft Inc. has upgraded Windows, bringing out major new releases roughly every 18 months, while Microsoft struggled for more than five years to produce the latest Windows iteration, Vista, which came out in January.

On Friday evening, Apple will release yet another new version of OS X, called Leopard, to replace the current version, known as Tiger. I’ve been testing Leopard, and while it is an evolutionary, not a revolutionary, release, I believe it builds on Apple’s quality advantage over Windows. In my view, Leopard is better and faster than Vista, with a set of new features that make Macs even easier to use.

Leopard will come preinstalled on all new Macs. It can also be purchased for $129 as an upgrade to existing Macs that, depending on configuration, can be as many as six years old. Unlike Vista, which is sold in four noncorporate upgrade versions ranging from a $100 stripped-down “basic” edition to a $259 deluxe “ultimate” edition, there’s only one version of Leopard. It includes all the features, from those aimed at novices to those aimed at power users.

For me, the marquee features in Leopard are a new function called Time Machine that automatically backs up your entire computer in the background; two new methods, called Cover Flow and Quick Look, for rapidly viewing the contents of files without opening any programs; and new techniques that allow you to access the files in, and to remotely control, other computers on your network or connected over the Internet with a few clicks and no technical expertise.

Plus, Apple’s free software for running Windows on a Mac, called Boot Camp, which was formerly an add-on users had to download and install, is now built right into the operating system. And, in my tests, the third-party Fusion program for running Windows and Mac programs simultaneously continued to work fine in Leopard.

I did notice a few drawbacks, but they were minor. The menu bar is now translucent, which can make it hard to see the items it contains if your desktop picture has dark areas at the top. The new folder icons are dull and flat and less attractive than Vista’s or their predecessors on the Mac. While Time Machine can perform backups over a network, the backup destination can only be a hard disk connected to a Mac running Leopard. And, on the Web, I ran into one site where the fonts on part of the page were illegible, a problem Apple says is known and rare and that I expect it will fix.

While Apple claims the new system includes more than 300 new features, there is nothing on the list that could be considered startling or a major breakthrough. Some of Leopard’s features are unique, but many others — such as backing up data and quickly viewing files — have been available on both Windows and the Mac via third-party programs or hard-to-find geeky methods buried in the operating systems. Leopard has made them easy to find and use.

When I upgraded my personal iMac desktop to Leopard, it took less than an hour, and after the process was complete, all my programs, including the Mac version of Microsoft Office, the Firefox Web browser and Adobe Reader, worked rapidly and fine. I was still able to run Windows XP via Fusion. And my previous installation of Boot Camp, which turns the iMac into a speedy, full-fledged Vista machine after a reboot, worked perfectly. All my Vista programs and files continued to function properly.

With Cover Flow, users get a visual preview of a computer’s files without having to open programs.

In fact, every piece of software and hardware I tried on two Leopard-equipped Macs — a loaned laptop from Apple and my own upgraded iMac — worked fine, exhibiting none of the compatibility problems that continue to plague Vista. My old Hewlett-Packard inkjet printer, for which Vista lacks the proper software, worked instantly in Leopard, even over the network. And, unlike with Vista, it was able to print on both sides of the page. I popped my old Verizon cellphone modem card into the test Leopard laptop and it worked, too, with no software installation or tweaking.

Leopard felt about as fast as Tiger, and it started up much faster than Vista in my tests. I compared a MacBook Pro laptop with Leopard preinstalled to a Sony Vaio laptop with Vista preinstalled. Even though I had cleared out all of the useless trial software Sony had placed on the Vaio, it still started up painfully slowly compared with the Leopard laptop.

It took the Vista machine nearly two minutes to perform a cold start and be ready to run, including connecting to my wireless network. The Leopard laptop was up, running and connected to the network in 38 seconds. In a test of restarting the two laptops after they had been running an email program, a Web browser and a word processor, the Sony with Vista took three minutes and 29 seconds, while the Apple running Leopard took one minute and five seconds.

Here’s a rundown of some of Leopard’s key features. Much more detailed information is available at apple.com/macosx.

File management: Apple’s Finder, the equivalent of Explorer in Windows, now offers two new ways to quickly see what your files contain. You can still view them as icons or lists. But you can also use Cover Flow, the same system Apple uses in iTunes and on the iPhone to display album covers for music. In Leopard, a large preview of each file you select appears above the list of files in a folder, and you can rapidly scroll through these icons. These previews are live, and their contents can be viewed without opening the program that is normally needed to display them.

Time Machine backs up files.

For instance, if the file is a video, you can just click on it, and it will play. If it’s a multipage PDF file, you can click on it, and arrows will appear allowing you to flip through the pages.

An even better and deeper look can be obtained using a feature called Quick Look. Just hit the space bar or click on a toolbar icon, and a preview of any selected file zooms out. You can even view multiple sheets in an Excel file via Quick Look without launching Excel.

Another quick new way to see your files is available in the Dock, the Mac’s equivalent of the Windows Task Bar. Here, any folder you place on the right side of the dock will display its contents, after a single click, either as a grid of icons displaying miniversions of the file or as a “fan,” or arc, of such icons. These special Dock folders are called “Stacks.” Leopard includes one by default that is the destination for everything you download from the Internet, so your desktop will no longer get cluttered with downloads,

Time Machine: This built-in feature will continuously back up all of the contents of your Mac to either an external hard drive directly connected to the computer, or to a hard disk connected to another Mac running Leopard that’s on your network. The initial backup, in my tests, took all night, but after that, the system updates the backups hourly and I didn’t notice any slowdown during the process.

To recover any file you deleted, you simply click on the Time Machine icon, and you are taken to a view that shows file folders — or your email or address book or photo collection — in a stack of windows that appear to go on infinitely. You click on an arrow and the stack of windows zooms until you arrive at the last view in which the missing file existed. Then, you click “restore,” and the file is recovered in your normal desktop view. You can also restore whole folders, groups of files, or even an entire hard disk.

Shared computers: In Leopard, any computer that has been set to be shared on your network shows up on the left side of every Finder window. Click on it, and you can access whatever folders have been shared on those machines. Depending on the remote computer’s security settings, you may first have to enter a user name and password. It’s the simplest method I’ve ever seen for accessing other computers on a network. And it works with Windows PCs as well as Macs. When I first turned on the Leopard laptop in my office, it immediately found a shared folder on my colleague’s old Dell running Windows XP. She hadn’t even remembered sharing the folder, which contained files from 2003.

You can copy or move files to and from these shared computers, or view their contents with Cover Flow and Quick Look, or open them in programs on your own computer.

If you are a member of Apple’s optional .Mac service, which costs $100 a year, you can use a feature called “Back to My Mac,” which can access your Macs from thousands of miles away over the Internet. However, this feature works only over certain kinds of routers (not all of them Apple’s) and, as my router didn’t qualify, I couldn’t test it.

Remote control: For any Mac in your shared-computers list for which you have permission, you can take over the screen by simply clicking on a button called “Share Screen.” You can also remotely control distant Macs over the Internet using Apple’s built-in iChat instant messaging program, as long as you have permission and the Macs are running Leopard.

Stacks displays the files in folders in the dock.

iChat: Apple now allows you to use its instant messaging program with Google Talk as well as AOL’s AIM service, and you can set up a video chat in which you can present a slide show or display a document. You can also add special backgrounds that can make it look as though you’re someplace else, like Paris. In my tests, this even worked with someone on the other end using a Windows XP computer running the latest version of AIM.

Spaces: In order to cut down desktop clutter, Leopard lets you set up as many as 16 different desktops that can run simultaneously, with different programs open in each. You switch among these desktops by using keyboard commands or a menu.

For instance, you might have your iPhoto and iTunes running in one “space,” or desktop, your Web browser and email program in another, and Windows XP in another.

Leopard isn’t a must-have for current Mac owners, but it adds a lot of value. For new Mac buyers, it makes switching even more attractive.

Email me at mossberg@wsj.com. Find all my columns and videos online free at the new All Things Digital web site, http://walt.allthingsd.com.

Back in January, when I reviewed the massive new operating system, which took more than five years to develop, I called it “unexciting” because many of the breakthrough features Microsoft had planned for it had been jettisoned, and most of the rest were already present in the rival Apple Macintosh operating system, OS X.

But I also said it was “worthy,” and better than prior versions of Windows, because it has a stronger security system under the hood and better integrated searching.

Over the ensuing months, however, Vista has proved to be a disappointment, even though Microsoft says it’s selling like hotcakes. Based on my own experience and on reports from readers, it’s clear that many Vista PCs start up more slowly than new PCs running its predecessor, Windows XP, or than even well-worn Macs. And there is still a significant compatibility problem: Too many software and hardware products still don’t run, or don’t run properly, with Vista.

So, if you’re shopping for a new Windows computer, one of your first decisions is whether you want to get Vista, which comes on almost all new models, or to stick with Windows XP. PC makers are still offering XP on a few new consumer PCs. For instance, Dell offers four consumer laptops and two consumer desktops that can be ordered with XP.

Buying XP will likely result in fewer frustrations in the short run. But buying Vista may be the better choice for the long run. Over time, more and more products will be released that are tailored to the new system.

Your other option is to shun the Windows dilemma and buy a Macintosh. I regard the Mac operating system as superior to Windows, and Apple embeds it in beautifully designed machines. Macs have been spared the plague of viruses and spyware that afflicts Windows, and have better built-in multimedia software.

But, if you’re thinking of buying a Mac, it makes sense to wait a few weeks or months to gauge the early reviews and user reactions to Apple’s own new version of its operating system, called Leopard, due out Oct. 26. After that date, Apple won’t build in the current version of OS X, called Tiger, on new machines.

Here are some tips if you’re shopping for a new Windows PC this fall. They apply to desktop PCs and to most mainstream laptops, though there are additional considerations, such as size and weight and battery life, for smaller laptops meant primarily for travel. As always, these recommendations are intended for average consumers doing average tasks, not for heavy gamers, video professionals, or corporate buyers.

Operating system: If you opt for Vista, the best choice for average consumers is a version called Home Premium, which includes all of the new graphics and multimedia features. Many low-end PCs have only a stripped-down version called Home Basic. Some people may need Vista Business, a version that can link to some kinds of corporate networks that the two Home varieties can’t. If your budget allows, you can get an expensive version called Ultimate that includes the features of both the Home and Business versions.

Junk software: Most Windows consumer models are stuffed with “craplets” — crippled trial versions of programs. They take up space and can slow down the machine. One way to avoid these is to buy a so-called business PC, like one of Dell’s new Vostro models. Dell also allows you to opt out of trial software, especially when ordering its pricier XPS models. Many other manufacturers make this hard or impossible, especially if you buy a PC at a retail store. But the stores may clean up a new PC for a fee.

Memory: Buy at least one gigabyte of memory for Home Basic and at least two gigabytes for all other Vista versions.

Video: Vista’s flashy graphical interface works best with a separate, or “discrete,” graphics card that has its own memory. Some “integrated” graphics systems work fine, too, but they claim some of your main memory via an approach called shared memory.

Processor: Any “dual-core” processor from Intel or AMD should be fine for Vista. Don’t worry about processor speed. Buying added memory does more for performance.

Hard drive: Don’t scrimp on storage space, unless you are absolutely certain you won’t be saving many photos, songs or videos. Even an average PC should come with 300 gigabytes of hard-disk space for a reasonable price.

Performance: If you’re shopping in a retail store, try to check the performance rating Microsoft builds into Vista. It’s available by clicking “Show more details” in Vista’s “Welcome Center” screen. If this rating is below 3.0 on a Home Premium model, avoid the computer. For best results, shoot for 3.5 or higher.

Price: You can get a bargain-basement computer for under $400. But, for a versatile Vista PC with Home Premium, two gigabytes of memory, discrete video, a large hard disk and a dual-core processor, you should expect to spend $800 or more.

Email me at mossberg@wsj.com. Find all my columns and videos online free at the new All Things Digital web site, http://walt.allthingsd.com.

Tomorrow, Apple Computer will introduce a new edition of the operating system for its Macintosh computers that finally solves the missing file problem, and introduces other features as well, including a new “Dashboard” that instantly displays small, frequently used programs like a calculator, dictionary and stock tracker.

The new release, called Tiger, is the latest version of Apple’s excellent Mac OS X operating system. Its key feature, called Spotlight, is the first universal, integrated search system ever offered as part of a mainstream consumer PC operating system. In seconds, Spotlight can peer inside e-mail, office documents of all kinds, photos, songs, address books, calendars, and all manner of other files to see which ones match a search term you type in.

Spotlight is vastly better than prior built-in search functions on either the Mac or on Microsoft’s Windows operating system. It also beats the add-on search programs for Windows. Spotlight can rapidly find almost any file, any time — even years after it was created, and even if it is hidden among tens of thousands of other files. So as users learn to trust it, they no longer will have to worry about where they store files and what they name them.

This is a big deal. Along with a similar built-in search capability Microsoft is working on for its next version of Windows, Spotlight could spark a major change in the way people use computers. Instead of hunting for documents or clicking on programs, people may now start activities by searching for relevant files and then opening them as needed.

Spotlight is only one of the impressive new features in Tiger, which will be free on all new Macs and will cost $129 for existing users. The others include the Dashboard feature; parental controls on what kids can do on the computer; dazzling built-in video conferencing; and a revised Web browser that allows private surfing and quick reading of news headlines.

Tiger’s built-in search system, Spotlight, finds soccer-related files (bottom) no matter where they’re stored on the Mac; the Dashboard feature (top) offers quick access to stock quotes, yellow pages, flight data and other information.

Overall, Tiger is the best and most advanced personal computer operating system on the market, despite a few drawbacks. It leaves Windows XP in the dust.

It also adds to the Mac’s general superiority over typical Windows computers as the best choice for average consumers doing the most common computing tasks. Apple’s hardware already was the best in the business, and Mac OS X has, so far, escaped the virus and spyware problems that plague Windows.

The new Apple system boasts some key capabilities Microsoft won’t introduce for another 18 months or so, when it finally rolls out its long-awaited next version of Windows, code-named Longhorn. Chief among these is the integrated, universal search. A second is “virtual folders,” called Smart Folders by Apple, which can automatically scoop up files that meet criteria you set.

In my tests, on three different Macs during the past couple of weeks, Tiger performed generally well. Installation took about an hour and went smoothly in each case. None of the computers ever crashed, and every program I tested worked fine, despite the change in operating-system versions.

The only significant problem I noticed was that the computers seemed to run into slight, but greater-than-normal, delays from time to time. Certain functions, like Spotlight searches and the updated Safari Web browser, were very fast. But with other tasks, I noticed more spinning beach-ball icons, Apple’s symbol for delays, than I had with the prior Panther version of the Mac operating system.

In particular, the built-in e-mail program, Apple Mail, was slower. There was a perceptible lag in opening a new e-mail form, beginning a reply, and displaying the drop-down contact list that appears when you begin typing in an e-mail address.

Apple acknowledges it will need to tweak Tiger to eliminate the delays, and it promises to address the problem within a few months. It might be wise for users with older, slower Mac models to wait until then to upgrade to Tiger.

The company claims Tiger has 200 new features. Here is a rundown of the most important ones.

Search: The new Spotlight search system can be summoned by just clicking on a small magnifying-glass icon that appears in every menu bar at the upper right. You simply start typing in a word or series of words, and as you type, an organized list of results instantly appears. The list tells you how many hits were found and displays the results in categories by file type, like e-mail messages, contacts, documents and so forth.

If you click on “Show All,” you get a larger window with a handsomely formatted list of results that you can organize by date, file type, person mentioned or other methods. Spotlight even finds words inside Adobe’s PDF files. It also can search on the data stored inside music and photo files, such as the names of artists and camera information. If picture files are found, thumbnails of them are displayed right in the list, and you can view them in a slide show.

Spotlight is far superior to add-on desktop search programs available for Microsoft Windows from Google and others, because it doesn’t have to constantly “index” the hard disk, looking for new files while the disk spins constantly. Since it is built deeply into the operating system, Spotlight learns about each new file as soon as it is created, saved or downloaded.

Prior built-in search functions in the Mac and Windows operating systems were slow and couldn’t search on some kinds of data, like e-mail. So you had to use separate search features in each type of program. Spotlight makes that unnecessary, though separate search functions are still available.

Dashboard: With the press of a single function key, a new translucent screen appears that holds large, stylish icons for useful little programs you might want to get to quickly. These programs, called Widgets, include a dictionary and thesaurus; a calculator; a weather display; a calendar; a language translator; a weights and measures converter; a stock tracker; an electronic yellow pages program; and a flight tracker.

These things are already available on the Web or through separate programs on many PCs. But with Dashboard, they pop up instantly, over whatever screen you are using, without disturbing any work you are doing. You don’t have to launch separate applications or employ a Web browser.

Apple ships 14 Widgets with Tiger, and starting tomorrow, the company will make available downloads of many more written by third parties. Some of these, already posted on other Web sites, include Web cam viewers, simple games, and small panels for searching encyclopedias.

Parental Controls: Tiger is the first operating system I have seen with built-in, system-wide parental controls. You can create a separate user account for a child that restricts his or her computing actions in a wide variety of ways.

Parents can limit what programs a child can launch and ban the child from burning CDs and DVDs, changing system preferences, or even printing.

You can restrict a child’s Web surfing to the sites you specify, and limit his or her exchanges of e-mails and instant messages to the people you specify. If anyone else sends the child an e-mail, it is forwarded to the parent. If the child wants to send an e-mail to a nonapproved person, the parent can be asked for permission electronically. The e-mail controls require both the child and the parent to be using Tiger.

Video Conferencing: If you have a video camera on your Mac, Tiger allows you to hold a video conference via its instant-messaging program with up to three other people simultaneously. Each participant is shown in a large panel of a handsome, three-panel display. I tested this, and it worked perfectly. Other built-in video chat systems, on Windows and earlier Mac operating systems, typically allow video conferencing with one other person.

Smart Folders: Tiger allows you to create special folders, which are, in effect, saved searches. For instance, you could set up a folder to hold all files containing the word “Fenway” that were created after a certain date and are above a certain size.

This kind of special folder isn’t a new idea. Apple has had them in its iPhoto and iTunes programs for awhile, and Microsoft included them in the latest version of its Outlook program. Third-party programs have them as well. But in Tiger, they can now be created right on the desktop, to capture many kinds of files, with no added software needed.

The only drawback is that you can’t directly turn a Spotlight search into a Smart Folder, and desktop Smart Folders can’t include some of the file types Spotlight can retrieve, including e-mails. Apple has added a separate Smart Folder feature to its built-in e-mail program.

Web Browsing: Apple’s built-in Safari Web browser was already better than Microsoft’s Internet Explorer, and in Tiger it is now much faster and has some great new features.

One is called Private Browsing, which allows you, with two clicks, to enter a mode where the browser doesn’t save most traces of which Web sites you visited.

Another is a built-in RSS reader. This function, usually found only in separate software programs, displays summaries of the latest headlines for items posted to many news sites and Web logs, or blogs. In Safari, these can be viewed right from within the browser, in pages that are formatted handsomely and can be sorted in various ways. Tiger even includes a screen saver that displays the latest headlines Safari has retrieved.

Security: The Mac already had a key security feature missing in Windows. On a Mac, most software installations require the ID and password of the computer’s owner. That makes it harder for digital criminals to carry out the kind of surreptitious software installations that place spyware on computers.

In Tiger, this has been ratcheted up a notch. When you download anything from the Internet using the Safari browser or Apple Mail program, Tiger examines the download for hidden application programs and warns if one is present. Unless the user approves the download, Tiger won’t save it to disk in a form that allows the application to open.

In addition, Tiger seeks the user’s permission any time any application program is run for the first time.

Automation: A new feature called Automator allows nonprogrammers to string together common tasks to automate them. For instance, you could create an automated sequence that would play certain songs, or retrieve and change certain photos. It’s a nice idea, but I found it too complicated for most average users.

In addition to the delay problem, I found one other small thing lacking in Tiger. The new version of Apple Mail, while sleeker looking, offers less information on what is happening in downloads of new mail, unless you bring up a special window.

Still, Tiger is a beautiful and powerful operating system that advances personal computing. It is a big gain for Mac users right out of the box. If Apple can wring out the delays, it will be a home run.

Write to Walter S. Mossberg at mossberg@wsj.com.