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.

In classrooms and offices, homes and coffee shops, Macs are far more visible in the U.S. than they were just a few years ago. Part of this success results from the fact that Macs are excellent machines that handle the most important and common tasks as well as — or better than — computers running Microsoft Windows.

But the new popularity of the Mac is also partly due to the fact that it can now run Windows along with Apple’s superior Mac OS X operating system. That means that if there’s a program you need that comes only in a Windows version, you can run it on any current Mac model, speedily and with all its features.

Starting next week, there will be a new way to do this. A company called VMWare, long the leader in what’s called “virtualization” — running multiple operating systems simultaneously on a single computer — will be selling a program called Fusion that allows Windows, and Windows programs, to run on a Mac.

I’ve been testing Fusion, and I’ve found it works well. For instance, as I write this column on a Mac laptop using the Mac version of Microsoft Word, Fusion is allowing me to simultaneously run several popular Windows programs — Microsoft Outlook, Windows Media Player and Internet Explorer. Each is running in its own window, just as if it were a native Mac program. I can switch from one to the other rapidly and smoothly. Their icons show up on the Mac’s “Dock,” just like the icons for Mac programs.

In my tests, Fusion never slowed down my MacBook Pro laptop or two other Macs on which I tested it. As I write this, the Mac version of Word and all three Windows programs are performing normally, even though I am also running five other Mac programs. My MacBook Pro, which isn’t the latest or most powerful model, has two gigabytes of memory and an Intel processor that is a generation behind the current model.

Fusion, which will be available for $80 at vmware.com, becomes the third major option for running Windows software on a Mac. It will go up against a fine program called Parallels Desktop, also available for $80 at parallels.com and at retail stores. The third option is Apple’s own Boot Camp, currently a free product available at apple.com/bootcamp. Boot Camp will become a built-in feature of the next version of Apple’s Mac OS X operating system, due in October.

All three programs require users to purchase a full version of Windows and install it on the Mac. Like Fusion, Parallels is a virtualization program that allows you to run Windows and Windows programs simultaneously with the Mac operating system and Mac programs. Boot Camp works differently: It requires that you restart the Mac to switch into Windows, and it runs only one of the operating systems at a time.

In my tests, I compared Fusion and Parallels, which is its closest competitor. I used Windows XP Professional. Each also works with the new Windows Vista (and with older versions of Windows and various versions of the Linux operating system). But Microsoft has imposed a legal prohibition on installing the most common consumer versions of Vista, Home Basic and Home Premium, via virtualization programs.

The two programs are very similar. In most scenarios, they function nearly identically. Both allow you to run the full Windows desktop either in a window on your Mac or in full-screen mode. Alternatively, both allow Windows programs to float on their own, with the Windows desktop hidden, so they look and feel just like Mac programs. Both permit you to fetch and save files from folders already on your Mac. Both support copying and pasting between Mac and Windows programs. Both automatically use your Mac’s Internet connection.

Parallels has more features than Fusion. It comes with a set of utilities Fusion lacks, such as a program that can migrate the contents of a physical Windows PC into a Parallels virtual Windows PC, and another that allows you to retrieve files from the virtual Windows machine even when Parallels isn’t running. Parallels also has a nice feature that lets you assign any file to automatically open in a Windows program instead of a Mac program. And it makes it much easier to use a printer over a network than Fusion does.

But I found Fusion puts less strain on the computer overall. While I like Parallels and have used it since it came out, it sometimes slows down my Mac, especially when it is starting up Windows or performing some other major task. Fusion has a much smaller impact on the Mac’s overall performance.

You won’t go wrong with either program. Both give the Macintosh a level of versatility that can’t be matched by Windows-only machines.

• 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.

But in the past few years, Apple has mounted a sneak attack on the Windows world. Its weapon has been the Windows version of iTunes, the free media organizing, recording and playback program that most people think of as just a companion to Apple’s iPod music and video players. I think of iTunes as the most subversive software on the Windows computer, not because it does users any harm or does anything underhanded, but because it is allowing Apple to subvert, from inside, Microsoft’s dominant platform position.

That’s because iTunes is much more than a companion to the iPod, much more than a media playback program and even more than a front door to Apple’s online download service. It’s a sort of miniplatform hiding right within Windows that allows Apple and other companies to connect a host of hardware and software, and to create media-sharing networks without engaging with Windows itself or with Microsoft’s built-in Windows Media Player.

There are way more copies of iTunes installed than were bundled with Apple’s 100 million or so iPods. In fact, at last week’s D: All Things Digital conference, Apple CEO Steve Jobs estimated more than 300 million copies of iTunes were installed. Many people download and use iTunes to play music and video, and to purchase media, for use on their computers, even if they don’t own iPods.

And the vast majority of iTunes installations, probably 90% or more, are on Windows computers, not Macs. Ironically, that makes Apple, Microsoft’s ancient rival, one of the biggest software developers for Windows.

Many people don’t realize that every time they install iTunes on a Windows PC, they also are installing Apple networking software called Bonjour, which operates independently from the Microsoft built-in network software controlled from the Windows Control Panel. This Apple network layer isn’t harmful and doesn’t interfere with the Microsoft networking functions. It’s designed to allow iTunes users to share their music.

Out of the box, each copy of iTunes looks for other shared iTunes music libraries on your local network. It doesn’t share your library unless you authorize it to do so. The user merely has to go into iTunes’ Preferences function (under the Edit menu in the Windows version), click on the Sharing tab and select “Share my library on my local network.” You can choose to share your entire library or just selected playlists. You can require people to enter a password to gain access, or not. You can also turn off the function that allows you to see others’ libraries.

If you use Sharing, you’ll see in iTunes’ left-hand panel a list of shared libraries on other iTunes-equipped computers on your local network, whether they reside on Windows or Macintosh computers. Clicking on these libraries allows you to play the songs they contain. It doesn’t allow you to transfer the song files among the computers.

In many homes, offices and college dorms, iTunes users have access to numerous libraries on nearby computers. For instance, as I write this on a Mac laptop in my home office, I am playing a song that resides on a Windows Vista desktop PC in another room. To achieve this feat, I didn’t have to fiddle with the often confusing network settings in the Windows Control Panel or in the Mac’s similar System Preferences program. I just had to use iTunes on both machines and click a couple of buttons.

In effect, each copy of iTunes, with the user’s permission, broadcasts a sort of beacon that signals its presence to other copies of iTunes on a local network, regardless of the operating system underneath. It makes the operating system irrelevant.

This independent iTunes networking capability goes way beyond sharing music among computers. A modified version of this function is what allows Apple’s new Apple TV product to fetch all the music and videos from all the computers in your house and play them back through your TV set — even if all those computers are Windows machines. It could also allow Apple’s forthcoming iPhone to wirelessly stream music and videos from computers on a local network, if Apple chose to build in such a function.

And the use of iTunes as a platform goes even beyond this networking ability. Small companies have released a slew of programs, such as iLike, last.FM, Mog and Nutsie, that read the iTunes library, with your permission. They use this information to determine your musical tastes and suggest new songs to try, to connect people with similar tastes, or to allow you to listen to your songs over the Internet.

Microsoft, its hardware partners and other third-party companies have achieved similar feats with other music programs and with hardware such as Xbox game consoles using similar sharing technologies. But the popularity of iTunes, and Apple’s position as Microsoft’s rival, makes the iTunes platform far more significant — and interesting.

• 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 latest, and most unusual, of these music phones has just been announced by Sprint. It’s a Samsung model called the UpStage. The UpStage costs just $149, less than a third of the iPhone’s planned $499 price, and it will go on sale early next month.

Samsung has shown real creativity in solving the problem of cramming a decent music player and phone into one small gadget. The slim UpStage has been designed with two distinct faces. On one side, it has a phone keypad and a small screen, for making voice calls and tapping out text messages. But if you turn it over, you see a larger screen and navigation controls, mainly for playing music, but also for other tasks, such as viewing online data.

Sprint’s UpStage music cellphone by Samsung.

At the same time, Sprint is slashing the price of songs sold on its proprietary music service from an outrageous $2.49 each to just 99 cents. That isn’t quite as cheap as it seems, because you have to pay $15 a month for the privilege of buying the 99-cent songs. But it’s still a positive step for consumers.

I’ve been testing the UpStage and found that its two-sided design works pretty well. It’s a better music phone, in my opinion, than Verizon’s Chocolate model, built by Samsung’s Korean rival, LG.

But the UpStage has too many weaknesses and compromises for me to recommend it. It has lousy battery life, both as a phone and as a music player, a limitation Sprint and Samsung have tried to offset with a free add-on that makes the phone too bulky. And it comes with so little memory that, out of the box, it can hold only around 20 average songs. Adding more capability costs extra, thus lessening the price advantage. There are other downsides as well.

I tested the UpStage primarily as a music player, because that’s its claim to fame. I compared it with the base-model iPod Nano, which also costs $149, although of course it doesn’t include a phone.

I did try out the basic phone stuff, like making calls, all of which seemed OK, though the screen on the phone side of the device is very small, a sort of throwback to early cellphones. Sound quality, reception and the keypad all were fine. The built-in 1.3 megapixel camera is standard for phones these days.

Only one of the phone’s two screens can be used at any one time, and you have to press a “flip” button on the side to switch. This worked well, but was kind of a pain when I was trying to use the keypad to type in text, like a Web password or the name of a new song playlist, on the music side of the phone. I had to flip to the side with the keypad and then flip back.

I loaded in about 20 songs and the UpStage played them back pretty well, displaying all the correct song information and album art. I also loaded in some photos, which also displayed fine, though the phone can handle only small picture files. I purchased a song from Sprint’s music service, and that downloaded and played well.

The only problems were that the album covers and photos looked grainy, because even the larger screen has pretty low resolution. And occasionally, the start of a song was clipped. The iPod Nano exhibits neither of these problems.

Out of the box, the UpStage comes with only a tiny memory card, which can hold only around 20 standard MP3 files. The iPod Nano can hold 500 of those files. To get the same capacity on the UpStage, you have to buy a larger, $40 memory card.

Though the UpStage is bigger than the iPod Nano, it has far worse battery life — just 2.5 hours of talk time for the phone and seven hours of music playback time, compared with up to 24 hours of music playback time for the Nano. To compensate, Sprint is throwing in a “battery wallet,” a case with an additional battery built in. This brings the talk time to 6.3 hours and music playback time to around 17 hours. But it makes the phone twice as thick.

There are two other problems with the UpStage. First, synchronizing its music with songs stored on a PC requires you to install and use Sprint music software. It doesn’t work with Windows Media Player or the Windows version of Apple iTunes, which most music lovers already own. (You also can manually drag and drop songs onto the phone’s memory card.)

Second, the navigation pad on the music side of the phone can be confusing. It works by touch controls; you have to use just the right pressure and slide your finger just the right distance along its sides to get it to work right. It’s too complicated.

Samsung and Sprint deserve credit for a good try with the UpStage. But it doesn’t quite cut it.

Email me at mossberg@wsj.com. See video versions of my reviews at wsj.com/mossbergvideo.

But, while YouTube is sometimes seen as synonymous with the Internet video revolution, there is a lot more to Web video. In fact, some of the most interesting video on the Web isn’t even the type of stuff that’s most popular on YouTube — short, one-off clips.

In various corners of the Web, people are producing real, episodic TV shows, including news, drama and comedy — sometimes with real actors and professional production values. Some of these longer-form, episodic shows are called video blogs, or vlogs, but others simply call themselves shows. Instead of lasting just a few minutes, they can run up to half an hour. These programs have more in common with regular broadcast and cable shows than with those emailed clips.

One of these days, a real hit show will emerge on the Web.

To be sure, such Web TV shows aren’t brand new. Ever since Apple began offering free video blogs on its iTunes store, people have been making them. One of the first to achieve popularity was a cheeky daily newscast called “Rocketboom,” which made a star of its first host, Amanda Congdon, who has moved to the ABC News Web site. (”Rocketboom” continues with another host.) Another was a comedy called “Tiki Bar TV.”

But the trend has accelerated and deepened lately, and a number of interesting sites have sprung up. My favorite is blip.tv, run by a team made up of a former systems administrator for the NHL, and a former TV news reporter and producer. Blip.tv (not to be confused with a similar-sounding site called bliptv.com) hosts a bunch of these new Web TV series, and also helps them attract funding, sponsors and advertisers. Anyone can upload a show.

One of my favorite shows available on blip.tv is called “Goodnight Burbank,” a comedy series about the squabbling that goes on behind the scenes at a local TV news show. Another is “Alive in Baghdad,” news reports from Americans and Iraqis on how the war affects average Iraqis. “Cube News 1″ is a series about life in the office cubicle. Other shows I’ve enjoyed on blip.tv include “HotRoast,” “The Ministry of Unknown Science” and “Josh Leo.”

Each show on blip.tv is accompanied by a profile page, comments from viewers and sometimes a blog. Many aren’t exclusive to the site. Some have their own Web sites, and episodes can also be found on YouTube and downloaded from iTunes and other sites. In fact, blip.tv provides links that make it easy to subscribe to shows on iTunes and other sites. But blip.tv does a good job of gathering a whole bunch of these Web TV series in one location.

Another good place to find these kinds of video blogs and Web TV series is at the iTunes Store. Unlike the music, commercial-TV shows and movies that Apple sells there, these Web video series are free. And because they are on iTunes, you can easily download them for viewing on a Windows or Macintosh computer, or on an iPod. You can even watch them on a real TV if you plug a computer or iPod into the set, or buy Apple’s forthcoming Apple TV product.

There are way too many Web series and video blogs on iTunes to list here, but if you go to the podcast page in the iTunes store and scroll down to Featured Video Podcasts, you can get an idea of what is available. iTunes includes several Web-only video series produced by the big TV networks, including a fascinating series from ABC called “The Day It Happened,” with historic footage on events such as the Kennedy assassination, the fall of the Berlin Wall and the wedding of Princess Diana.

Another site worth watching is brightcove.com, from a company whose main business is selling the technology for doing Web videos to big media concerns, including Dow Jones & Co., the publisher of this newspaper. But brightcove also hosts Web video from average folks and small outfits. It will soon introduce a feature to allow average users to record video directly to its Web site and then mix it, legally, with clips licensed from big media companies.

Yet another worthwhile site is Network2.tv, which attempts to aggregate a wide variety of Web videos in one place.

I’ve only scratched the surface of the available video sites, but if you like YouTube, you may love what else is out there.

• Email me at mossberg@wsj.com. See video versions of my reviews at wsj.com/mossbergvideo.