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.

The most tangible example of this new approach is Dell’s XPS One desktop — an elegant, handsome, cleverly designed one-piece computer. If it didn’t have the Dell logo on it, the XPS One might be mistaken for a product of the PC industry’s design leaders, Apple or Sony.

Like Apple’s iconic iMac, the XPS One looks like it’s simply a sleek, flat-panel monitor. The guts of the computer have been stuffed into the back of the screen.

But this new Dell is no mere iMac clone. It makes its own style statement, even though it shares the same 20-inch widescreen display and a similar Intel dual-core processor with the base-model iMac. Where the iMac is squarish and silver, the XPS One is all black and rectangular, with speakers attached to the sides and a wide glass base. It looks more like a small TV set than a computer and, in fact, comes with a built-in TV tuner.

In my tests, I found the XPS One to be much better designed and equipped than Gateway’s iMac competitor, also called the One. In fact, the Dell XPS One is the first Windows all-in-one desktop I’ve tested that I believe matches or exceeds the iMac in hardware design. That’s no small feat, especially coming from Dell.

Unlike the Apple, for example, the Dell has a built-in slot for camera memory cards. It comes standard with a wireless keyboard and mouse, which cost extra on the iMac. Its screen can be turned off with the touch of a button without turning off the computer itself. Its USB and headphone ports are arrayed conveniently on the side, instead of mainly at the rear, as on the iMac.

And, when you wave your hand in front of the black border to the right of the screen on the XPS One, a set of blue, back-lit touch controls magically appear for controlling the playback of music or video. They go away after a few seconds. The Dell also comes with a free year of 10 gigabytes of online backup.

For my tests, I used the least expensive standard configuration of the XPS One, which can be ordered for $1,499 at dell.com/theonepc. It came with two gigabytes of memory (twice the comparable iMac’s standard amount), a 250 gigabyte hard disk and Wi-Fi wireless networking, unusual in Windows desktops.

The computer performed crisply and well for me. I installed several popular third-party programs that weren’t included, such as Microsoft Office, the Firefox Web browser, Apple’s iTunes and Adobe Reader. All worked fine.

I also successfully tested the built-in TV function, which requires a cumbersome external attachment to work with a cable box. I was able to view and record TV shows, something you can’t do out of the box on an iMac.

I still recommend the iMac over the XPS One for several reasons other than hardware design. First, there’s the software. I believe Apple’s operating system, Leopard, is superior to the new Windows Vista operating system, the only choice on the XPS One. In my tests, a reboot of the XPS One took more than twice as long as a reboot of the iMac.

And I regard Apple’s built-in software, especially the iLife multimedia suite, as superior to the Dell’s built-in software, which includes a group of Adobe multimedia programs that are less well integrated and more complex.

The XPS One, unlike the iMac, also came with a bunch of craplets — trial software like Yahoo Music and come-ons for online services like NetZero.

Second, the iMac, unlike the Dell, is immune to the vast majority of malicious software floating around, so you don’t have to run annoying, memory-hogging security programs. The first time I turned on the beautiful Dell I was met with a warning that I had “multiple security problems,” and was led to install a security suite in a complex and tedious process.

Third, defying popular perception, the iMac costs less than the XPS One. The base, 20-inch iMac costs $1,199 — about $300 less. And even if you double the memory, and add a wireless keyboard and mouse to match the Dell, it’s still $1,399 — $100 less than the base XPS One (though Dell is currently running a sale that wipes out the $100 gap). Even the cheapest iMac has a dedicated video card with its own memory, something the base XPS One lacks.

Plus, while Dell offers only 20-inch screens on the XPS One, Apple has higher-end iMacs with huge 24-inch screens for the same price, or less, than the higher-end Dells.

Still, if you want a stylish Windows Vista machine that runs well and won’t cost a fortune, the XPS One fits the bill, despite its unlikely heritage.

• 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.

It gets better. This new PC, called Zonbu, from a new company of the same name, automatically receives free updates of its software when new versions come out. It doesn’t require antivirus or other security programs because it runs on the Linux operating system, which has attracted very few viruses or spyware programs. And it takes up almost no room — it’s a tiny little box.

Zonbu’s overall goal is to vastly simplify the process of buying and using a computer. The idea is to make it not only more affordable, but also much less of a hassle and much more energy efficient.

I’ve been testing the Zonbu, and it does work. Its software is still in beta, or test, mode until next month. But you can buy it right now at Zonbu.com with free software updates into the future. However, there’s a catch — several catches, in fact. Some have to do with the machine’s design and pricing, and others with its performance. Taken together, they prevent me from recommending this computer, despite its intriguing price and concept.

The biggest catch is that the Zonbu computer doesn’t include a hard disk for storing files (that’s one reason it uses so little energy). Instead, all of your files are stored online on the company’s servers. That offers several advantages, such as the fact that the files are automatically backed up.

But you have to pay for that online storage. In fact, to get the $99 price for the Zonbu computer, you have to commit to a two-year contract at prices ranging from $12.95 a month for a relatively small 25 gigabytes of storage to $19.95 a month for 100 gigabytes. If you opt to pay month to month instead of two years in advance, the Zonbu will cost you $249.

To get the Zonbu for $99 with 100 gig-abytes of storage, it will cost you $517.95 up-front after the discount of three free months that the company is currently offering. And the Zonbu doesn’t come with a monitor, keyboard, mouse, Wi-Fi adapter, speakers or DVD drive.

By comparison, you can get a Dell Inspiron 531s for just $529, after rebate. It has twice the memory, a DVD drive and a much better processor than the Zonbu. And it comes with a screen, keyboard, speakers and mouse — oh, and a 160-gigabyte hard disk that requires no monthly fee.

To be fair, the Dell doesn’t come with a full-fledged office productivity suite, while the Zonbu has OpenOffice, a competitor to Microsoft Office, preloaded. To get OpenOffice on the Dell, you must download and install it.

Also, the Zonbu monthly service fee is offset by some savings. The $99 machine uses so much less energy than a typical PC that the company claims you could save noticeably on your electric bill. And you might also save the cost of subscribing to security software updates.

Zonbu

Because the Zonbu stores your files on a remote server, you can also use them remotely, at no extra cost, from another Zonbu or from any Windows PC.

To speed things up — and guard against an Internet service outage — the built-in programs are stored locally on the computer, and Zonbu includes a small 4 gigabyte memory card in the machine to cache your documents. In my tests, this allowed me to keep using the Zonbu even when I unplugged it from the Internet.

In addition to OpenOffice, the Zonbu comes with the Firefox Web browser, an Outlook clone called Evolution, an iTunes clone called Banshee, the Skype Internet phone software, and a bunch of other programs for organizing photos, playing video and more. There are also some casual games.

To Zonbu’s credit, the machine is capable of recognizing lots of printers and digital cameras, out of the box. It worked well with my Kodak camera and Hewlett-Packard printer.

But there are three other big problems with the Zonbu, problems that belie its goal of eliminating hassles. First, you aren’t allowed to install any added software. You’re stuck with what the company provides. And that means, for instance, no video-editing software, for now at least.

Second, a lot of this Linux software is rough, below the polished level of Windows or Mac programs. In my tests, various programs crashed or froze frequently. While the Banshee program is supposed to work with iPods, it failed to work properly with both of the iPods I tested.

Finally, I found that the Zonbu crawled much of the time. Folders took forever to open, email took way too long to appear, and so forth. And I was testing it on a very fast Internet connection. This may be because of the very wimpy processor Zonbu uses to save money and energy.

I strongly support Zonbu’s goals of making computing simpler, cheaper and more energy efficient. But this product has too many compromises.

• 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.

You could, of course, automatically back up your files to an external hard disk, attached to your PC or to your home network. But that can get expensive, and it doesn’t store your backup remotely, so any disaster at your home or office could also wipe out your backup drive.

There’s another method: backing up over the Internet to a remote server somewhere. This is automated and solves the location issue, but in too many cases it has been costly and complicated, usually with quotas on how much you can back up.

Now, things are changing. I have been testing two online backup services that offer unlimited capacity — no quotas or limits at all — for around $50 a year.

One, called Carbonite, has been unlimited from the start, and Mozy, which previously had limits, is offering unlimited capacity as of today.

Mozy and Carbonite can be set to back up only a few key folders or types of files — say, all your work documents or music files — or, you can set them to back up nearly everything on your computer. If you have a loss, whether a single file, a folder, or everything, they allow you to recover it. Also, you can back up multiple computers with Mozy and Carbonite, but you have to pay extra for each additional machine.

The two services are easy to set up and easy to use. Each worked fine in my tests, both for backing up my key files and also for restoring them.

Carbonite can be downloaded at www.carbonite.com or purchased in stores. There is a 15-day free trial, after which it costs $50 a year, though some stores also sell a $15 version that lasts for three months. The trial version doesn’t back up music or videos by default.

Mozy can be downloaded from www.mozy.com and costs $4.95 a month, or $54.45 if you pay for a year in advance. Mozy also has a totally free version, which is limited to two gigabytes of data. (That is likely to be more than enough, by the way, to cover all of a typical consumer’s word processing, tax and budget files, and plenty of photos.)

Both services currently run only on Windows XP, but both expect to work on the new Windows Vista operating system. And both companies plan to release Macintosh versions next year.

Each installs a fairly small program on your PC that constantly works in the background to back up your data. When a file changes, or a new file is added, it is queued for backup. Carbonite backs up new or changed files 10 minutes after you save and close them, but only backs up each file once a day. Mozy checks the hard disk every two hours and backs up everything that is new or changed. With Mozy, but not with Carbonite, you can also opt for a scheduled backup at a time and interval of your choosing.

The biggest drawbacks of these two products are that backups can be very slow, especially the first backup, and you must have Internet access to do backups and to restore your files. In my tests, on a very fast Internet connection, it still took many hours to do a fairly small initial backup with each product, consisting of about five gigabytes in one case and under two gigabytes in another. A larger backup could take days, though subsequent backups would be much, much quicker.

Both companies encrypt the backed-up files and say they don’t view them. Both try to avoid overburdening or slowing down your computer and Internet connection by going idle or slowing down when you are using your computer for other tasks.

To restore files with Carbonite, you open a sort of virtual representation of your backed-up files and click on what you want restored. If your computer is stolen or not functioning, you can also go to a Web site to initiate a full restore to a new computer.

With Mozy, you can also restore files and folders via a virtual view of your backup that resides on your PC. But Mozy has a much richer Web interface for viewing your backup and for restoring files. From a Web site on any PC, you can log into Mozy and pick any file or folder to retrieve. I even logged in from a Mac, opened a Mozy backup of my Windows PC, and recovered a photo that was then downloaded to the Mac.

Of the two products, I prefer Mozy. Carbonite is a little quicker and simpler to set up, but it’s more limited. If you want to go beyond the default backup choice — your most common documents and settings — you have to troll through your hard disk to select additional folders and files for backup. Mozy also has a default setting, but makes it much easier to alter or customize it.

Mozy offers more-versatile restoring and scheduled backups, and unlike Carbonite, will back up an external hard disk. Mozy will also send you a DVD of all your files, for a fee. Carbonite won’t. Mozy also keeps multiple versions of any file for 30 days. Carbonite doesn’t.

Still, you won’t go wrong with either of these two services, and you’ll sleep better at night.

Email me at mossberg@wsj.com.