As I noted in my Windows XP Professional x64 Edition Preview, Microsoft has been working on a version of XP for x64 hardware for almost two years now. Much has changed since Microsoft tentatively announced support for the fledgling computer platform in April 2003. First, the x64 platform has shown enormous street creds, with Intel essentially copying AMD's original design, thus assuring that x64, and not Itanium, would be the mainstream 64-bit computing platform of the future. Second, Microsoft has elevated XP x64, its desktop-oriented x64 operating system, from being a niche player to being the basis for its next mainstream OS platform.

Early versions of XP x64 weren't pretty and lacked significant functionality. But more recent releases, like the Release Candidate 1 (RC1) build the company issued last fall and the RC2 version that shipped earlier this month, show a maturity and attention to detail that was previously missing. XP x64 is still a subset, of sorts, of XP 32-bit, but the missing features in XP x64 were dropped with good reason.

For example, XP x64 includes no 16-bit subsystem, so legacy MS-DOS and 16-bit Windows applications will not run on this system. Compatibility purists may look at that omission as a problem, but I agree with Microsoft's assessment that dropping 16-bit support is a chance to rid the system of messy legacy deadwood.

Also missing are legacy networking protocols such as NetBEUI and AppleTalk. Again, the chance to clean house, so to speak, should be applauded not condemned, even if it temporarily limits the size of the potential audience for this release. These are unnecessary technologies today, and Microsoft, understandably, doesn't want to support them forever.

In short, XP x64 looks and acts like the 32-bit version of XP Pro with Service Pack 2 (SP2). Virtually everything you see in a default XP Pro system is present in XP x64, including the Security Center, with just a few exceptions. There are also occasional features in XP x64 that aren't present in XP SP2, such as a 64-bit version of Internet Explorer. On the other hand, XP x64 also includes a 32-bit version of IE 6 for compatibility reasons: All the browser add-ons IE users take for granted will not work in IE x64. And as I'll discuss momentarily, compatibility issues are, in fact, almost the only major differentiator between XP x64 and XP Pro 32-bit.

In this preview of Windows XP Professional x64 Edition, I'll focus on the Release Candidate 2 (RC2) build of this product and highlight what I feel will be the most important adoption blockers for this OS release. In my eventual review of the product, I'll provide a more traditional step-by-step overview of its many features and compare it more closely with 32-bit XP versions.

My test system

In September 2004, I purchased a Hewlett-Packard (HP) Pavilion a640n desktop computer. This system shipped with an AMD Athlon 64 3400+ processor, 512 MB of RAM, a 160 GB hard drive, an NVIDIA-based Lancer FX5200XT video card (128 MB), integrated LAN and sound, two CD-type drives (DVD+RW and CD-ROM), and a nice 9-in-1 media reader.

I upgraded two components before making the a640n my main desktop over time. First, I replaced the lackluster Lancer video card with an ATI Radeon 9800 Pro (128 MB), which is more suitable for gaming. Then, I added another 512 MB of RAM to bump the system up to a full gigabyte of memory. I also upgraded the installed version of XP Home to XP Pro (32-bit). Through the end of 2004, I essentially multiple-booted the system between several versions of Windows, including XP Pro, two pre-release builds of Windows Server 2003 x64, and two pre-release builds of XP x64.

When Microsoft released Windows XP x64 RC1, I wiped out the system and dual-booted between XP Pro and XP x64. Then, in February 2005, I wiped it out again, and I'm now running only XP x64 RC2 on the system, though I expect to eventually add an XP Pro partition for various compatibility reasons. My goal, however, is to live in a pure x64 environment for as long as possible to see if it's doable.

Compatibility

The site you're now visiting, Paul Thurrott's SuperSite for Windows, began life in August 1998 as the Windows NT 5.0 SuperSite. I started the site because I was I was excited about Microsoft's plans to move the NT kernel into mainstream Windows versions. NT 5.0, of course, became Windows 2000 a few months after that (and then Microsoft began talking up a final Windows 9x version, then code-named Millennium, so I changed the site name to the more general Windows SuperSite. At Microsoft's request, I later changed the name again to SuperSite for Windows.)

Back then, compatibility was a key issue for any Windows user considering NT. Specifically, you had two choices: The compatibility that came with Windows 9x, or the stability of Windows NT 4.0. Conversely, Windows 9x wasn't very stable at all. And Windows NT 4.0 wasn't very compatible with hardware or software. I recall printing out a portion of the NT 4.0 Hardware Compatibility List (HCL) every time I visited Best Buy, Fry's, or whatever, looking for a new network interface card (NIC) or other hardware component. Otherwise, you could find yourself out of luck. I wrote about the compatibility of Windows NT 5.0 Beta 2 in a showcase article way back in September 1998, and it's interesting to see how that experience is being mirrored today again with XP x64.

Anyway, with Windows 2000, of course, the compatibility gap closed, and Windows XP finally gave Windows users the best of both worlds: A single OS that was as compatible as possible with Windows 9x and as stable as Windows NT 4.0. For the past few years, we haven't really seen the Windows market bifurcated as it was during the 9x/NT 4.0 days.

And now we have the x64 platform. Essentially an inelegant solution to a classic problem, x64 provides Windows users with a 64-bit environment that is backwards-compatible, for the most part, with the 32-bit software we run today. It also provides the full processing power of the underlying hardware, whether you're running 32-bit or 64-bit code, a feature the 64-bit Itanium sorely lacks. The problem, however, is that x64 is again splitting the Windows world, this time into 32-bit (x86) and 64-bit camps. On the 32-bit side, we have the full compatibility with all the hardware and software we've been using for years. On the 64-bit side, well ...

Not so good. Windows XP Professional x64 Edition is largely compatible with the 32-bit software we run today, though I've found glaring exceptions in the several months I've been testing pre-release versions of the system, including entire categories of hugely important software applications, like antivirus solutions. But XP x64 is not compatible with the multitudes of 32-bit hardware drivers that are currently available for every single device under the sun. So if XP x64 doesn't ship with a device driver for a particular piece of hardware you own, you have to pray that the manufacturer has created its own driver. As of this writing, very few have.

So. Once again, we have a split Windows market. On the left, we present the 32-bit versions of Windows XP, which offer the best hardware and software compatibility of any modern Windows operating system. And on the left, we have XP x64. This operating system is more stable and more secure than its 32-bit brothers, and can take advantage of significantly more hardware and software resources. However, it is not compatible with many of the software applications and applets, and hardware devices that you probably already own. This issue, more than anything, will determine whether XP x64 is a success or failure. Let's take a look at hardware and software compatibility separately.

Hardware compatibility

Hardware compatibility can be a killer, especially if you can't find a driver for a critical device, like a video card. Early builds of XP x64 didn't support the NVIDIA graphics card or the RelTek-based embedded sound card in my system, but I was able to locate beta versions of both. When I swapped in the ATI video card, however, XP x64 supported it automatically.

With the RC2 release, the audio card still wasn't supported, but RelTek was nice enough to post a brand new x64-compatible driver earlier this month, and that installed without a hitch. And as someone who still recalls the uneasiness of device support during the NT 4.0 days, I can state firmly that, with x64, there's just nothing like a clean Device Manager. So far so good.

However, when I begin adding other hardware devices, things don't go so well. My HP ScanJet 3970 scanner, for example, is not supported. My Canopus ADVC-50 analog-to-digital video converter is hopeless. And my Dell 1700n printer, which is network-attached, will not install using Dell's software, even though, oddly enough, it runs and completes Setup.

These are some of the types of devices people will need to work with using XP x64. Since both HP and Dell are major Microsoft partners, and those devices are reasonably new, I expect them to eventually be supported. But I wonder about the Canopus device. As of right now, I am trying to work around these issues. Since the Dell printer is really just a rebranded Lexmark printer, I installed drivers for the closest Lexmark model XP x64 supports natively, and they appear to work. And I can attach the scanner to one of my many other PCs. But most people don't have the home office set up I have. Those people would be left in the lurch by XP x64, or at least be forced to dual boot with XP 32-bit.

Other devices, like my iPods, work fine, which I guess makes sense since they're probably just seen as generic mass storage devices by the underlying system. The a640n's 9-in-1 media reader was automatically recognized exactly as it is in XP 32-bit, which is nice. I'll have more to say about hardware devices in my final review of this product.

Software compatibility

Software compatibility in XP x64, currently, is a disaster. Don't get me wrong: Most 32-bit applications do indeed install and run on XP x64 just fine. But I suspect that most people who try out this system over the next several months will be irritated to find that one of more crucial applications will not install at all, and that alone will give many a bad experience. Most of them, I suspect, will run right back to XP 32-bit.

I don't blame them. In my own admittedly unscientific testing, XP x64 simply wouldn't install some of the important applications that I rely on regularly. Inexplicably, most of them are Microsoft applications (Go figure). This should be profoundly embarrassing to the software giant, and hopefully someone at the company will ensure that all of its currently supported applications are patched to be x64 savvy by the time XP x64 is finalized. How can it expect third parties to work on x64 compatibility if Microsoft ignores it?

There are three main reasons for software incompatibility on x64, according to Microsoft. First, some applications are still using old-fashioned 16-bit installers, even though the applications themselves are 32-bit; since XP x64 doesn't support 16-bit applications, you can't install them on that system. Second, many applications are poorly written to test for specific versions of the operating system, and since they see XP x64 as being newer, or different in some other way, to XP 32-bit, they simply refuse to install. I've tried XP x64's compatibility fix feature to try and get around this issue, but I've never been successful. Third, some applications actually let you install them, but then later check the OS version, so they don't run. These applications, presumably, could be "fixed" using the aforementioned application compatibility fix feature, but I haven't run into one yet to test.

When I install a new system, I run through a list of "always install" applications, which are highlighted in the table below. These are all of the applications I install first on every one of my system, because I use them regularly. As you can see from the list, XP x64's success rate was mixed. Most applications worked fine. But some of the ones that didn't are critical to me.

Application Installs? Runs? Notes
Adobe Acrobat Reader 5.1 Yes Yes Works normally. (I don't like or use the 6.x and 7.x versions of Adobe Reader because they're too slow.)
Adobe PhotoShop Elements 3.0 Yes * Yes Installs but displays failure dialog (Figure) while attempting to install Windows Media 9 Series codecs. Application then runs normally. A software update to version 3.01 also installed and ran fine.
Adobe Premiere Elements 1.0 Yes * Yes Installs but displays failure dialog while attempting to install Windows Media 9 Series codecs. Application then runs normally.
Apple iPod installer Yes Yes Works normally.
Apple iTunes 4.7.1 Yes Yes Works normally.
Executive Software Diskeeper 9 Pro Yes * No This application appeared to install normally, but when you run the application, it loads the stock XP x64 disk defragger. An update to a newer version failed to install (Figure).
Microsoft Digital Image Suite 10 CD Yes Yes Works normally.
Microsoft MSN 9 Premium Yes Yes Works normally.
Microsoft MSN Messenger 6.2 Yes Yes Works normally.
Microsoft Virtual PC 2004 No n/a Setup fails, citing "Fatal Error." (Figure).
Microsoft Cmd Here Powertoy No n/a Setup incorrectly identifies OS version and fails (Figure).
Microsoft Windows AntiSpyware Beta 1 (February 2005 version) Yes Yes Works normally.
Microsoft MSN Messenger 7.0 Beta Yes Yes Works normally.
Microsoft PhotoStory 3 No n/a Setup incorrectly identifies OS version and fails (Figure).
Microsoft TweakUI PowerToy No n/a Setup fails and recommends running the 64-bit version, which doesn't (yet) exist. (Figure).
Microsoft WMP 10 Energy Bliss Viz Yes Yes Works normally.
Microsoft Office 2003 Professional (includes Word, Excel, PowerPoint, Outlook, Publisher, Access, InfoPath) Yes Yes Works normally.
Microsoft FrontPage 2003 Yes Yes Works normally.
Microsoft OneNote 2003 Yes Yes Works normally.
Microsoft Office 2003 Service Pack 1 (SP1) Yes * Yes Confusingly displays two error messages during Setup (Figure) but then runs normally.
Microsoft OneNote 2003 SP1 Yes * Yes Confusingly displays an error message during Setup (Figure) but then runs normally.
Mozilla Firefox 1.0 Yes Yes Works normally.
Macromedia FlashPlayer 7 (for Firefox) Yes Yes Works normally.
Nero Burning ROM 6.6.0.3 Yes Yes Works normally.
PKWare SecureZIP 8.00.0018 Yes Partially * Installs normally, but doesn't create the contextual menu links I rely on, so it provides reduced functionality when compared to running on XP 32-bit.
Webroot Spy Sweeper 3.5.0.194 Yes Yes Works normally.
Zone Alarm Suite 55.062.011 No n/a Will not install (Figure).

In addition to presenting this small subset of available x86 applications, I should note that XP x64 is incompatible with entire classes of applications, including antivirus applications and security suites (but not, curiously, antispyware solutions). Microsoft tells that these antivirus applications won't work in XP x64 because they access the system's kernel, which is 32-bit code in XP 32-bit but 64-bits in x64. However, all major AV vendors, including Symantec and McAfee, are allegedly working on x64-compatible upgrades. (Let's hope they don't charge existing customers for them.) In the meantime, it's hugely stupid to run any Windows version without antivirus protection. I've only found one AV application--avast! antivirus 4.6 that comes in an x64 version. So I've installed the free Home Edition of this product in order to get some protection, but I'm not certain it's all that great yet. It's no Zone Alarm Suite, to be sure, but I presume it's better than nothing.

I also installed a large number of recently released video games, most of which worked just fine. Specifically, I installed Half-Life 2 (and the Steam application), Star Wars: Battlefront, Unreal Tournament 2004, Far Cry, DOOM 3, Painkiller, and Painkiller: Battle Out of Hell. All of these titles installed without a hitch, and most appear to run just fine. (I'm actually playing through the Painkiller expansion pack, Battle Out of Hell, for the first time now on the x64 system. It's been rock-solid.) DOOM 3 and Far Cry, however, wouldn't run initially. After I finally caved and installed ATI's beta video drivers, DOOM 3 started up without a hitch. But Far Cry refused to run. A day later, I mistakenly clicked on the Far Cry icon in the Start Menu while reaching for FrontPage. It ran, and ran fine. I have no idea why.

Aside from these peculiarities, the fear with games is that XP x64 won't perform as well as its 32-bit brethren. This hasn't been the case in my experience. After replacing a 2.8 GHz Pentium 4 Dell machine with the a640n running XP 32-bit, I noticed that the x64 hardware performed better in games (and was quieter to boot), despite the lower clock speed of the AMD chip in the a640n. Interestingly I used the same ATI video card in both setups, so the comparison is even more relevant. And when I moved the x64 system to XP x64, I didn't notice any drop in performance at all. The key here, naturally, is properly written video drivers. Today's hardware accelerated 3D games task the video card as much as they do the CPU, if not more.

I noted previously that the a640n originally shipped with an NVIDIA video card. Though NVIDIA should be lauded for regularly releasing beta versions of its x64-compatible video card drivers, I had problems with several revisions of them, resulting in slow screen refreshes and other graphical glitches. It's been a while since I've tested an NVIDIA card in this system, and I'm certainly not going to do so now, given the excellent results I've gotten with the ATI card. But NVIDIA gamers are advised to keep up on that company's x64 drivers. Some versions are better than others.

Some final thoughts on compatibility

For now, Microsoft can talk up the technical superiority of XP x64 all it wants, but compatibility issues are going to sink this operating system faster than you can say Microsoft Bob. There is little doubt that x64 is the future of desktop computing, but attempting to move to XP x64 will prove to be a fruitless trip for many people. To its credit, the software giant is being very clear about the near niche nature of its first x64-based desktop operating system, and the company has repeatedly told me that XP x64 is really just aimed at technical workstations, business desktop users, and enthusiasts.

Based on this information, and my own experience, I must issue a cautionary note to readers: If you're thinking about migrating to XP x64 immediately, don't. Instead, evaluate the RC2 version in a dual-boot scenario with XP 32-bit first. Test all of your important hardware and software and make sure they work, or at least work well enough. And do so knowing that, even if everything appears to work fine, it's possible that a desirable hardware device or software application will appear this year that simply won't work in XP x64.

These issues will diminish over time, of course. Hardware makers, hopefully, will surprise me and show up with vast reams of x64-compatible drivers and support the new system immediately. Sure, that's never happened before but you never know. Antivirus makers will suddenly vault into the x64 era with new XP x64 conversions of their popular and much-needed solutions. And all those 16-bit installers will slide silently into the sunset, never to bother us again. You never know.

Timing and availability

Windows XP Professional x64 Edition Release Candidate 2 (RC2) is currently available as a free download on the Microsoft Web site. In case it's not obvious, this version of XP will only run on x64-compatible hardware, that is, PCs with an AMD64 (Athlon 64 or Opteron) or Intel EM64T (Pentium 4 6XXX or Xeon) microprocessor. Microsoft expects to finalize XP x64 in March and then make the product widely available in April. The company will also offer a technology trade-up program for users with x64 hardware. I'll discuss details of this program in my eventual review of XP x64.

Conclusions

Windows XP Professional x64 Edition Release Candidate 2 (RC2) is a rousing technological achievement, a near-perfect migration of Windows XP Professional to a 64-bit code base that doesn't sacrifice performance for 64-bit capabilities. But while XP x64 is far more compatible with hardware and software than its Itanium-based predecessor, it is also not compatible enough to meet the needs of average users. Therefore, most XP users should stick with XP 32-bit through at least the end of 2005.

If you're a technology enthusiast with the right hardware, however, XP x64 offers a chance to live on the edge in a way that hasn't been possible for Windows users since the HCL-wielding days of NT 4. With XP x64, Microsoft has provided a superb technological base for the next several years, one that will likely become the mainstream computing platform during the Longhorn time frame. Like a faraway land full of treasure real or imagined in an age of explorers, XP x64 is there for the brave and foolhardy. Are you up to the challenge?