Though there's no good method of telling in advance how easy--or nightmarish--upgrading to Windows XP will be, here's some advice that applies to almost everybody:
Prepare to patch regularly using Windows Update. We recommend you set it to "auto-update". You can also visit the Windows XP Home Edition Upgrade Centre to determine if your computer is worthy of an upgrade.

In the months since Microsoft launched the XP operating system--to a fairly cordial reception, judging from reports showing early sales approaching those of Windows 98--we have encountered or heard about dozens of glitches and pitfalls. In some cases, the fixes began rolling out along with the OS itself. Other problems will almost certainly be addressed in an initial service pack. Microsoft has released SP1 earlier last year.  Make sure a new CD is for Windows XP Upgrade, SP1.

The day it shipped Windows XP, Microsoft posted multiple bug fixes, compatibility updates, and enhancements on its Windows Update Web site--more than 18MB of them, all told. The same day, Microsoft's Knowledge Base support site also listed hundreds of confirmed bugs found in Windows XP, many of which still don't have patches or solutions. And the company's general-purpose Windows XP newsgroup continues to receive thousands of new posts every day.

Some of the updates are important. The 1.9MB Windows XP Update Package, October 25, 2001, for example, includes fixes for bugs in such new and vaunted XP features as its CD burning software, the Files and Settings Transfer Wizard, Remote Assistance, and Windows Messenger's audio and video tools. Separate updates to the CPU drivers for mobile Pentium III-based systems and Athlon-based systems enable those chips' power management features to function under Windows XP.

Not all of the updates are essential--or even desirable--for every Windows XP system, however. The fine print describing most of the patches warns that you should download and install them only if you're experiencing the problem described. Consequently most of us will probably opt to skip the 3.3MB update to Windows Movie Maker, which is recommended only for people who want to capture higher-quality digital video.

For many users, however, problems within the OS itself are less pressing than compatibility problems with hardware devices and with third-party software.

Process/program	Problem	Fix
CD burning	CDs recorded using Windows XP are unreadable or are missing files or folders when read in Windows 95/98 or in an MP3 player.	Update available from Windows Update.
Power management	Pentium III and Athlon power management features are not supported, resulting in shorter-than-expected notebook battery life.	Update available from Windows Update. See details for Pentium III and Athlon.
Shutdown	During shutdown, the computer occasionally freezes when the screen displays a 'Saving your settings' message.	Update available from Windows Update Product Catalogue. (Look in Start, All Programs, Windows Update, choose Personalize Windows Update, and click Display the link to the Windows Update Catalogue.)
AOL 6.x	Some versions are incompatible with Windows XP.	Upgrade to AOL 7.0 or to a compatible version of AOL 6.0x.
Ghost 2001	Program is incompatible with Windows XP.	Upgrade to Ghost 2002 ($50).1
McAfee VirusScan (through 5.21)	Program is incompatible with Windows XP.	For versions 4.5 through 5.21, download the application compatibility update from Windows Update (compatibility not verified by product manufacturer). Earlier versions must upgrade to version 6.0x ($40).1
Outlook Express	Files and Settings Transfer Wizard (for migrating to XP from an older Windows PC) loses account data or overwrites an existing account; or when run on the Windows 9x/Me PC, it corrupts the message store.	Update available from Windows Update.
PowerQuest Drive Image	Program is incompatible with Windows XP.	Upgrade to Drive Image 5.0 ($50).1
PowerQuest PartitionMagic	Program is incompatible with Windows XP.	Upgrade to PartitionMagic 7.0 ($50).1
QuickTime 5	Program doesn't launch automatically to play associated clips embedded in Web pages.	Download an IE 6 compatibility plug-in from Apple.
Remote Assistance	Remote Assistance fails when the system requesting help has more than one network connection (such as a network adapter and a modem) with Personal Firewall enabled.	Update available from Windows Update.
Roxio Easy CD Creator	Program is incompatible with Windows XP.	For version 5.0 Platinum, download the free version 5.1 update from Roxio's Web site. For version 5.0 Basic, download the 90-day trial of 5.1 Platinum, and use it until the Free 5.1 Basic upgrade appears. For version 4.02, download Windows Update (compatibility not verified by product manufacturer).
Symantec Norton AntiVirus 2001	Program is incompatible with Windows XP.	Download the application compatibility update from Windows Update (compatibility not verified by product manufacturer) or upgrade to Norton AntiVirus 2002 ($30).1
Symantec WinFax Pro 10	Program is incompatible with Windows XP.	Upgrade to WinFax Pro 10.02 ($50).1
Windows Messenger	Voice and video chat modes are incompatible with Internet Connection Sharing and/or ICS Firewall.	None.
Windows Messenger	Audio is marred by popping and echoing.	Update available from Windows Update.
ZoneAlarm Pro	Some versions block all Internet access or cause the computer to reboot spontaneously.	Update to version 2.6.357 or later by clicking the Configure button and then Check for Updates.

¹List price; discounts and rebates may be available. Prices in US Funds.

Like previous Windows upgrades, the new OS lacks support for many legacy devices, particularly printers and scanners. Windows 2000 drivers available from manufacturers' Web sites work well in many instances, though not in every case. But even when Windows XP does support a particular device, the driver may be capable of only bare-bones performance or compatibility (especially if it's a driver for a graphics adapter). That's why it's always a good idea to check Windows Update or the manufacturer's Web site for more-recent XP-compatible versions after you upgrade.

Though most 32-bit Windows programs do run under Windows XP, a few of them--notably, antivirus software, CD-burning tools, and drive-partitioning and -imaging utilities--won't work with Windows XP unless you upgrade them. As we went to press, a handful of major programs remained partly or completely incompatible. Roxio's Easy CD Creator 5.0 is among the most notable examples. Even though Roxio itself wrote the CD-RW driver built into Windows XP, the company had not yet posted the promised XP-compatible update for the basic version that ships with many new PCs (though an upgrade for the Platinum version sold in stores finally appeared in early November).

Complicating the issue are Microsoft's own application compatibility updates. One of Microsoft's October 25 patches was a 2.2MB download that made XP compatible with applications such as McAfee's VirusScan 4.5, 5.16, and 5.21; Roxio's Easy CD Creator 4.02 (that's right, Microsoft made a fix for the earlier version but not for the later one); and Symantec's Norton AntiVirus 2001. The update also solved a heartbreaking problem for young media hounds: In its shipped form, Windows XP is unable to play Disney's Snow White and the Seven Dwarfs DVD (a problem that to Microsoft's knowledge does not affect other DVDs).

Though most compatibility upgrades are free, some are not. And if you rely on Symantec's WinFax Pro 10.02, PowerQuest's PartitionMagic or Drive Image, or a few other programs that need costly upgrades, your software bill for achieving Windows XP compatibility could run hundreds of dollars beyond the cost of the OS itself.

Microsoft has yet to address several reported bugs. Many upgraders report that Windows Messenger's voice chat feature fails to connect, even when other instant messaging programs, such as Yahoo Messenger or an earlier version of MSN Messenger, work fine. Numerous other Windows XP users report that the operating system forgets your Explorer window view preferences (so you have to re-enter them every time you launch Explorer), and that the Taskbar tool tips (such as the one that shows you the date when you hold the mouse over the clock) display behind the Taskbar instead of on top, where they would be readable. Others report that Windows Update itself is forgetful, offering users patches that they have already downloaded.

Like many previous Windows versions, XP occasionally freezes when shutting down. As we went to press, Microsoft's Knowledge Base reported that an interim fix was available only by calling the company's product support number. And although the dreaded blue screen of death has been swept under the rug, Windows XP is not crash-proof. If a deadly driver or application incompatibility crashes the computer, the OS simply reboots by default (nostalgic users can revert to the old blue screen via a Control Panel/System setting). I met with this problem when I tried running non-XP-compatible versions of ZoneAlarm Pro and Easy CD Creator.

Early XP adopters have run into a few other glitches that don't quite qualify as bugs. The most prevalent is a simple problem afflicting Outlook Express users: In many cases, the upgrade process fails to transfer existing mailboxes to the XP version. The mailboxes from the old setup are still on the computer, but users must either move them to the current message store location manually or reconfigure Outlook Express to look for the files where they stand.

What do all these pitfalls add up to? A version of Windows that is starting to look a lot like previous ones, upgrade-wise. Interface glitches, incompatible applications, missing drivers, shutdown problems, crashing--these classic upgrade snafus have plagued just about every version of Windows that Microsoft has produced.

And just as with previous versions, Microsoft has indicated that a follow-on to Windows XP is in the works. The ETA: no later than 2004.

• Windows Update
• Microsoft Knowledge Base
• Microsoft Product Support for Windows XP. 1-800-668-7975
  (installation and two subsequent incidents free; $35 per incident for subsequent calls)
• Windows XP newsgroup
• Roxio Windows XP updates
• Symantec Windows XP compatibility
• Creative Labs XP drivers

Windows XP's anti-piracy technology has apparently been hacked. Officials of the British software security company BitArts Ltd. say that, within hours of the operating system's launch on October 25, software to bypass the Product Activation feature was already circulating on the Internet.

John Safa, BitArts' chief technology officer, reports that his company has identified two main approaches to hacking Product Activation. One involves comparing the volume-license version of XP (which doesn't use Product Activation at all) to the single-copy code and extracting the other files in the single-copy versions. The second approach uses a patch to trick the OS into believing that the user is always only one day into the 30-day window allowed before an upgrade version of XP must be activated.

Either way, the user is spared being nagged to activate. ( PC World is withholding technical details of the hack.)

Microsoft product manager Chandler Myrick says that the company is aware of these attempts to work around Product Activation, but he believes that relatively few Windows XP upgraders will locate and use them. "One of the primary goals for WPA was just to reduce casual copying," Myrick says. "And we think that even though these circumventions are available, WPA is going to do what we intended it to do for the vast majority of users."

Safa says it's a shame that Microsoft isn't using anti-piracy technology that really works, because it should in theory make software cheaper for paying customers.

"You either get it working 100 percent, or you don't bother," he says.