You might be able to get at the desired file if you have previously uploaded it to an online storage or photo-sharing service, or emailed it to yourself. But, in many cases, you could be stuck.

Now Dell (DELL), the big computer maker, is aiming to solve that problem with a new service called Dell Remote Access. Despite the name, the service can be installed on any brand of Windows PC running Windows XP or Windows Vista to make its files remotely accessible, as long as it has a broadband connection. You can transfer, or stream, or share these files with others. You can even remotely use the host computer’s Web camera.

And some of the service’s functions also work even if your remote device is one of Apple’s (AAPL) Macintosh computers or iPhones, or a computer powered by the Linux operating system, like Dell’s own Mini netbook.

For basic functionality — making the files on one Windows PC remotely accessible from other devices — Dell Remote Access is free. If you want to use its advanced functions, like the ability to remotely control the host PC or to access other devices on your home network, it costs $9.95 a month, or $99 a year. This paid version of the service also includes the ability to share with others access to files or to devices on your network, such as stand-alone Web cameras.

You only need to install special software on the host PC whose files are to be remotely accessed. For basic file access, the remote devices require just a Web browser and a password to tap into the host computer. You can download the software, and get started with the service, at dellremoteaccess.com.

I’ve been testing Dell Remote Access for a few days, at home and on the road, and found that it works well, despite a few glitches and limitations. It’s not revolutionary — many other services and software programs do part or all of what it does, with varying degrees of technical difficulty and at varying fees — but Dell Remote Access combines a wide variety of functions into a fairly simple package. It will be available as a preinstalled option on Dell’s PCs later this year.

Dell also is hoping it will give a boost to sales of its Mini line of very small machines with limited internal storage for files.

For my tests, I installed Dell Remote Access on my home Dell desktop, an XPS One model running Windows Vista. The installation was easy and quick, except for one oddity: To use the new service, you have to uninstall a network diagnostic utility Dell installs on its machines, called Dell Network Assistant. Since I had little or no use for the utility, this was no big loss, but if you rely on it, this conflict could pose a problem.

Next, I used the Remote Access software to select folders I wanted to make remotely accessible. By default, the program assumes you want to share your documents, music and pictures folders, but I added some others. The software tests your network connection to let you know how well it’s likely to work.

I used a variety of remote devices to access this home Dell. These included a Sony (SNE) Vaio laptop running Vista, a Mac laptop and an Apple iPhone. I even tried accessing the Dell machine from a virtual Windows XP installation running on the Mac.

Some of these tests were conducted from within my home network and others were conducted from across the country.

In general, the tests went well. With the Sony laptop, and within Windows XP running on the Mac, I was able to view photos and slide shows, and stream music and videos, from the Dell in all locations. I opened Microsoft Office (MSFT) files and PDF files remotely and transferred files to the remote machines. I was even able to remotely control the Dell at decent speeds and use the Dell’s built-in camera.

The only annoyance was that every time you want to remotely control the host machine, you must download and install a small utility. You also have to leave on your home computer.

Dell’s system provides more limited functionality if your remote machine is a Mac using Apple’s operating system, or a Linux machine or a mobile phone. With these setups, you can only view, stream or transfer files only from the main host computer. You can’t do remote control or view cameras.

But these limited functions did work pretty well on the Mac and the iPhone, although in some cases I had to first download a song to the Mac before it would play, rather than simply streaming it directly from the Dell.

But Microsoft Word documents stored on the Dell opened right up on the Mac. It was particularly impressive to be able to view a document or photo stored on the Dell from an iPhone thousands of miles away.

Dell Remote Access is a worthy service that’s worth a try.

Find all of Walt Mossberg’s columns and videos online, free, at the All Things Digital Web site, walt.allthingsd.com. Email him at mossberg@wsj.com.

The first approach uses a feature called Boot Camp that comes free on every new Mac. Using Boot Camp, the entire Mac is turned into a Windows PC, with the full capabilities and speed of a standard Windows machine. No trace of the Mac operating system is left running. The downside is that you can’t run Windows and Mac programs side by side.

The second approach uses one of two third-party programs to create a virtual Windows PC inside your Mac. This faux Windows machine runs at normal speeds and can operate simultaneously with the Mac’s own operating system. Programs native to each operating system can run side by side. The downside is that, because Windows doesn’t get complete control of the computer’s hardware, it isn’t quite as fast as in Boot Camp, and a few of its functions, like 3D graphics, don’t work as well.

This latter method is enabled by two excellent, closely matched $80 programs: Parallels, from a Swiss-based company of the same name, and Fusion, from VMWare, a U.S. company. It is Fusion that just got better, because VMWare just issued version 2.0 of the product with lots of new features, some of which let it catch up to the older Parallels and some of which push it ahead.

I’ve been testing Fusion 2.0 for a couple of weeks on two different Macs, and using it to run both Windows XP and Windows Vista. My verdict is that while you won’t go wrong with Parallels, Fusion edges it out as the better product.

The new Fusion 2.0 is a free upgrade for owners of version 1.0. It can be obtained at vmware.com/mac and at various retailers.

Like Boot Camp and Parallels, Fusion requires you to obtain and install a fresh, boxed, full version of Windows on your Mac. But once you’ve done that, your Mac becomes two computers in one. If you need to run programs that are available only on Windows, you can do so with ease.

For instance, as I write this column on a MacBook pro laptop, using a Macintosh word processor, I am using Fusion 2.0 to simultaneously run Google’s new Chrome browser, which is so far available for Windows only. I can switch between the two with a couple of keystrokes and copy text from one to the other.

Like Parallels, Fusion allows you to run Windows programs in one of three ways. You can see the entire Windows desktop, with Windows programs running within it, inside its own window on your Mac. Or, using a feature called “Unity,” each Windows program can float free, as if it were just another Mac program, with the Windows desktop invisible. If you minimize a Windows program, it disappears into an icon in the Mac’s Dock, just as Mac programs do.

Finally, you can devote the entire screen to the Windows desktop and hide the Mac operating system entirely.

Parallels can also do these things. Both programs can now also “mirror” your most common Windows and Mac file folders so that, for instance, all of the files in your Mac’s Pictures folder also appear in the My Pictures folder in Windows XP. This is a new addition to Fusion, as is the ability to take multiple “snapshots” of your Windows virtual machine, so if something goes wrong, you can roll back to a previous state when things were stable.

But Fusion has some other features Parallels lacks. For example, it allows you to automatically take those protective snapshots at timed intervals. It also permits you to completely customize keyboard commands so that the same common key combinations work in both Windows and Mac programs. It allows the faux Windows machine to take full advantage of multiple monitors, if you have them.

Fusion also uses a more modern and capable version of the proprietary 3-D graphics system in Windows, called DirectX. That means some Windows-only games and other programs that won’t work in Parallels will work in Fusion. I successfully tested two such programs, both from Microsoft: Worldwide Telescope and Photosynth.

And, in my experience, Fusion is a bit faster than Parallels. Both programs put a strain on your Mac when performing major tasks, like starting up or shutting down Windows. But Fusion seems to affect the Mac less. And, unlike Parallels, it can make Windows quicker by optionally assigning it control of the multiple “cores” in most modern processor chips.

Fusion also offers a one-year free subscription to Windows security software, while Parallels offers only a six-month subscription.

However, Fusion has its limits. Like Parallels, it cannot run the 3-D visual effects in Windows Vista. And, in my tests, it wouldn’t allow Windows running on one of my Macs to use the printer that was configured on the Mac, although that feature did work on my other test Mac.

In my view, Fusion is now the better choice for running Windows on a Mac virtually.

Find all of Walt Mossberg’s columns and videos online, free, at the All Things Digital Web site, walt.allthingsd.com.

Write to Walt Mossberg at mossberg@wsj.com

This contrast has appeared sharper in recent years, as Microsoft’s Windows Vista operating system received a tepid critical response compared with Apple’s Leopard platform and as the company’s Live Web search service has slipped further behind Google’s. In addition, Microsoft’s cellphone software, Windows Mobile, looks old and creaky compared with Apple’s sleek iPhone and Google’s forthcoming Android mobile operating system.

But innovation does exist at Microsoft’s sprawling Redmond, Wash., campus. For instance, last year’s daring and radical redesign of Microsoft Office has been a critical and commercial success.

Now, there’s a sort of guerrilla team inside Microsoft designed to churn out innovative products more often and more rapidly. Called Live Labs, the unit is a small operation that aims to turn technology theories into real, Web-based products relatively quickly. It has only about 125 employees, and even that modest number is broken up into smaller teams tackling specific projects.

This week, Microsoft Live Labs is releasing its first broad consumer Web service, called Photosynth. This service turns multiple photos of a scene or site — say, an art gallery or a building — into a 3-D scene you can virtually “walk” through on the Web.

Unlike a simple 2-D panorama, which many photo programs can create from several pictures, a Photosynth creation, called a “synth,” is a virtual 3-D environment. It gives you the feeling you are in the middle of a room looking around, or circumnavigating a building or object. You can travel through a scene both laterally and vertically, and zoom in to see detailed, higher-resolution views of objects inside the synth, such as paintings on a wall.

For instance, you don’t just see a long, flat picture of Stonehenge or the Grand Canal in Venice. You are made to feel you are there, moving through these places, looking up at the sky or down at the ground, and pausing to examine more closely a particular stone, boat or building.

Such 3-D walk-through images have been around for awhile; they are used on some real-estate Web sites, for example, to show houses virtually. But Photosynth allows anyone to create them using any standard digital camera, and even using pictures you already possess that weren’t created with Photosynth in mind. You could even use photos of the same site taken by several people. The software will analyze the pictures, figure out which ones overlap and in what order, and then turn those shots that match up into a 3-D synth.

Photosynth, based on technology Microsoft acquired in 2006, is entirely free, and it’s entirely based on the Web, at photosynth.net (where it will be launched at midnight EST Thursday). At that site you can view not only your own synths, but the synths created by every other Photosynth user.

I’ve been testing this service for about a week, and while it has its flaws, I believe that Photosynth offers a dramatic new way to use your photos and to share them with others.

Photosynth works within a Web browser, using a small plug-in you install. Currently, it works only in Windows, using Microsoft’s own Internet Explorer browser or its rival, Firefox. A Macintosh version is in the works, but for now, you can’t even view others’ synths in the Mac operating system.

When Photosynth works right, the results are wonderfully satisfying. But it takes some skill to get a set of photos the service can match up well, a quality Microsoft calls being “synthy.” Ideally, portions of each slice of a 3-D scene should show up in at least three photos, with 50% overlap between them. After you upload your pictures and Photosynth does its best to make them into a 3-D scene, the service assigns them a percentage number that indicates how synthy they were.

In my tests, I tried both collections of photos I already possessed and some I snapped with Photosynth in mind. My pictures of a piazza in Verona, Italy, were only 38% synthy, while ones I took of a hotel room specifically for Photosynth use were 73% synthy.

One gripe I had was that Photosynth doesn’t tell you how synthy your pictures are until after you have uploaded them and waited until the system merges them, a process that can take a long time over a slow Internet connection. It would be much better if the service could tell you in advance how synthy the pictures are. Another objection is that Photosynth has no privacy settings. All your synths are open to viewing by everyone who uses the service.

But, overall, Photosynth is an impressive new way to view and share photos, and an encouraging sign that innovation and creativity still live in Redmond.

Find all of Walt Mossberg’s columns and videos online, free, at the All Things Digital Web site, walt.allthingsd.com. Email him at mossberg@wsj.com.