If you're concerned about compatibility, Windows Vista is mostly good news. And that's not unexpected, given Microsoft's overwhelming commitment to compatibility. Arguably, Windows would be far more elegant today were Microsoft not so dedicated to keeping 1980's-era software like VisiCalc running well beyond its Stay Fresh date. But proponents of backwards compatibility continue to prevail over calls for something completely new.

Looking back, Microsoft's last truly new operating system was Windows NT, and that shipped in 1993. But even NT included compatibility bits to make it more appealing, including the ability to run OS/2 applications and a look and feel that mimicked that of Windows. Today, Windows Vista is a continuation of the NT line of products, and not something completely new. As you might expect from an evolutionary upgrade, Windows Vista offers excellent backwards compatibility, both from a hardware and software perspective.

That said, chances are you're going to run into occasional problems, especially if you move to Vista quickly. But the situation with both hardware and software compatibility will improve over time. And Vista includes technology, as did XP, to allow the system to emulate older Windows versions. This usually works wonders when an application won't install correctly, though it's not perfect.

Also, users who choose to install the x64 versions of Windows Vista will be in for some especially nasty surprises, though I'm amazed to note that these systems offer far better hardware compatibility than I would have imagined. Sadly, many applications won't install or work correctly on x64 Vista versions, and for this reason, I feel that most users should forego x64 for the time being or at least test an x64 Vista version thoroughly before committing. I'll look more closely at x64-specific issues throughout this part of the review.

Hardware compatibility

One of the best things about Windows is that you can go into any Best Buy, CompUSA, or other retailer, buy any hardware device in the store, bring it home, and know it's just going to work. On the flipside, one of the worst things about a new version of Windows is that the previous statement no longer applies. I recall wandering down the aisles of a Best Buy in Phoenix ten years ago when Windows NT 4.0 first shipped, with a copy of the NT Hardware Compatibility List (HCL) in my hand: I needed a network adapter, but had to be sure I got one of the few models that worked in the new system.

Windows Vista users face a similar problem today, though there are some differences. First, there's no HCL, at least not a public one, so you're a bit more on your own when it comes to discovering what's going to work. Second, Vista is already far more compatible with existing hardware than was NT a decade ago. Indeed, Microsoft tells me that Vista is actually more compatible with today's hardware than Windows XP was five years ago. Based on my testing, I believe it.

I've been testing Windows Vista on a variety of systems, including two desktops (both of which use x64-compatible CPUs, one of which is dual core), two Media Center PCs, three notebooks, and a Tablet PC. Vista's out of the box compatibility with the built-in devices on each system has been stellar. (In this case, "out of the box" refers both to the drivers that actually ship on the Vista DVD as well as the drivers that are automatically installed via Automatic Updates the first time you boot into your new Vista desktop.) On virtually all of these systems, Vista found and installed drivers for every single device in or attached to the system.

There are some exceptions, of course. The Lenovo ThinkPad T60p that is my primary notebook computer includes some esoteric hardware that Vista can't figure out, including an internal EV-DO wireless modem and a biometric processor that's part of its embedded fingerprint reader. And that's about it.

And about those fears that Vista's high-end Aero user interface would require hardware upgrades? Balderdash. On every single one of my systems, except for a four-year-old Toshiba Tablet PC that was slow the day it came out of the factory, Aero is enabled by default and works just fine.

Where you might run into problems is with older scanners, printers, and similar peripherals. My network-attached Dell laser printer still doesn't have any Vista drivers, but since it's a Lexmark in disguise, I was able to get it up and running just fine with just its IP address and the model number of the Lexmark machine it really is. I have an older HP Scanjet 3970 that requires a cruel bit of software to work properly, and Vista just doesn't know what to do with it. But my Epson Stylus Photo 900 works just fine, and even uses Epson's bizarre configuration utility even though I never installed the software manually myself.

TV tuner hardware? It just works. Zune? Done. Apple's iPods? They all work. PlaysForSure devices? Of course. They're all seamless, and they even work with Sync Center. What's amazing is that this hardware compatibility prowess extends right to the x64 versions of Vista. For the most part, if it works out of the box in Vista 32-bit versions, it will work in x64 as well.

Software compatibility

While I can't possibly test even a decent sampling of the Windows compatible software that's available today, I do use what I feel is a representative collection of mostly modern software regularly. In the sections below, I step through my experiences with this software on the 32-bit version of Windows Vista Ultimate. Later, I'll provide a quicker overview of the x64 (64-bit) experience. I've broken this overview down into two parts: Applications and games.

Applications

I run a standard set of applications across most of my desktop and mobile PCs. Here's what I've been running (or trying to run) on the RTM version of Windows Vista. I'm still doing some testing, so I may update the applications that are marked as "n/a," which means I haven't attempted an install yet on the final shipping version of Vista.

Application 32-bit 64-bit (x64)
Adobe Acrobat Standard 7 Works fine. n/a
Adobe Photoshop Elements 5.0 Works fine. n/a
Adobe Premiere Elements 3.0 Works fine. n/a
Adobe Reader 8 Works fine. Works fine.
Apple iTunes 7 Works fine. Works fine, though I had to install QuickTime first
Apple QuickTime Player 7 Works fine. Works fine.
AVG 7.5 Free/Professional Both work fine. The free version of AVG anti-virus does not work on Vista x64, but the Professional version works fine.
Flickr Uploadr 2.3 Works fine. The application installs and works but the Flickr Uploader shell extensions are nowhere to be seen.
Google Picasa 2 Works fine. Works fine.
LeechFTP Works fine. Works fine.
Microsoft Digital Image Suite 2006 Suite Works fine. Works fine.
Microsoft Office 2003 Professional Works fine. n/a
Microsoft Office 2007 Professional and Enteprise Works fine. Works fine.
Microsoft Photo Story 3.1 Works fine. Works fine.
Microsoft Virtual PC 2007 Beta Works fine. Works fine.
32-bit version works fine. Works fine. Works fine.
64-bit version works fine. Works fine. Works fine.
Microsoft Visual Web Developer 2005 Express with Visual Studio SP1 and Vista patch Works fine. Will not install.
Microsoft Windows Mobile Device Center Beta Works fine. Works fine.
Microsoft Windows Live Messenger 8.0/8.1 Beta Works fine. Works fine.
Mozilla Firefox 2.0 Works fine. Works fine.
Nero 7.5.7 Works fine. Works fine.
New York Times Reader Works fine. Works fine.
Skype Works fine. n/a
Slysoft AnyDVD Works fine. Works fine.
Slysoft CloneDVD Works fine. n/a
Slysoft CloneDVD Mobile Works fine. Works fine.
TechSmith Camtasia 3 Works fine. n/a
TechSmith SnagIt 8 Works fine. Works fine.
uTorrent Works fine. Works fine.
Verizon VZAccess Works fine. n/a
Windows Live OneCare 1.5 Beta Works fine. Will not install.
WinRAR 3.6 Works fine. Works fine (including the shell extensions).
Zune Works fine. Software installs and works fine. I did not attempt a device sync.

Games

As I did after Windows Vista Release Candidate 1 (RC1) shipped a few months ago, I began testing a series of popular video games to see how they fared under the final version of Windows Vista. The results, as expected, were largely positive: Not only do most Windows XP-compatible games work just fine under Windows Vista, most of them also integrate automatically into Vista's new Games Explorer as well. Unless it's a very new game designed specifically for Windows Vista, you won't get performance information there as you do with built-in games, but the ESRB information is enough to let parents lock kids out of violent video games using Vista's parental controls features. It's a nice touch.

In addition to raw compatibility, I was also interested to see how games performed under Vista. While I don't benchmark games (or other software) per se, I can say from an unscientific standpoint that games perform roughly as well on 32-bit versions of Vista as they do on Windows XP. I've read that Microsoft expects to see games perform under Vista to within 10 or 15 percent of their performance under XP, and that sounds about right. For the short term, gamers will want to stick with XP if they're concerned solely about performance. However, over time, as faster processors, DirectX 10-based video cards, and even Vista-specific games appear, gamers will switch from XP to Vista just as they once switched from Windows 98 to XP. This transition should occur within a year.

As far as games are concerned, I tested the game titles in the following table under 32-bit versions of Windows Vista on a single desktop PC with an ATI graphics chipset. In each case, games were run at the highest-possible resolution my hardware supported (1920 x 1200, the native resolution of my display) and with maximum graphics effects enabled. In some cases (DOOM III for example), I was forced to run at a lower resolution because the game didn't support my display's native resolution. All games were updated with the latest software updates.

Game Games Explorer integration Notes
Call of Duty Yes Ran and performed normally.
Call of Duty 2 Yes Ran and performed normally.
DOOM 3 Yes I experienced serious graphical glitches that made this game unplayable. I suspect these issues are related to the graphics driver, because Microsoft says this title should run fine in Vista.
Far Cry Yes Ran and performed normally.
Half-Life No Ran and performed normally, though Games Explorer was unable to provide box art or ESRB rating.
Half-Life 2 Yes Ran and performed normally.
Half-Life 2: Episode One No Ran and performed normally, though Games Explorer was unable to provide box art or ESRB rating.
Halo: Combat Evolved Yes Ran and performed normally after manually downloading a Vista compatibility patch from the Bungie Web site.
LEGO Star Wars II: The Original Trilogy Yes Ran and performed normally.
Quake 4 Yes See notes for DOOM 3: This title suffered from identical issues.
Sin Episodes: Emergence No Ran and performed normally.
Unreal Tournament 2004 Yes Ran and performed normally.

Incidentally, I did test a few of these games on the 64-bit version of Windows Vista Ultimate. But since I didn't test the full range of games listed above, I don't feel comfortable arriving at any conclusion about this scenario just yet. I can say that the games I did test, like Unreal Tournament 2004, run just fine under Vista x64 and integrated properly with the Games Explorer.

Some more notes on the x64 versions of Windows Vista

Put simply, running a 64-bit (x64) version of Windows Vista does not make sense for most people, though I suspect that will change over time. While the Vista x64 versions surprised me with their excellent hardware compatibility--a claim I'd never make about Windows XP Professional x64 Edition--nagging software compatibility issues ultimately sunk any hopes I had of moving to the 64-bit system.

That's too bad, because the x64 versions of Windows Vista include enhanced security features that will never be back ported to the 32-bit versions. Until the compatibility issues are resolved however, it's not worth worrying about that. Unless you're running a limited set of applications, compatibility generally trumps security, and the security of 32-bit Vista versions is generally excellent anyway.

But if it makes you feel any better, at least consider some other aspects of this equation. First, to truly take advantage of a 64-bit operating system, you'd need more than 4 GB of RAM and applications that are specially written to access that much memory. Today, there are no mainstream applications like that, and even Adobe's high-end CS3 suite of applications won't be 64-bit enabled. And second, Vista x64 also removes some legacy subsystems that you might find useful. The most crucial is the 16-bit MS-DOS subsystem, which is still required for many application installers, even those for some 32-bit applications. This, too, is a compatibility issue, of course. No surprise there.

Compatibility Conclusions

Overall, Windows Vista's hardware and software compatibility is excellent, but the devil is in the details: For the short term, at least, chances are good that you'll own some hardware device--a printer, scanner, or whatever--that doesn't work properly. Software compatibility is better, much better on the 32-bit Vista versions, however. My recommendation for those contemplating 64-bit is simple: Wait. Though the 64-bit versions of Windows Vista will ultimately provide better security and, with the proper memory upgrades and compatible high-end applications, more head room than the 32-bit versions, those gains are more than offset by painful software incompatibilities. It's getting better, there's no doubt about that. But for now, I'd steer clear of 64-bit Vista versions unless you really know what you're doing.