The case of the completely incompatible

The nightmare
I upgraded to Windows XP because everyone said it was more stable, but they forgot to tell me that a lot of my software and hardware wouldn't work with the new OS. Ninety percent of my software isn't compatible with XP, and I still can't get my scanner to work right, despite installing all kinds of patches.

Analysis
When we queried CNET readers about XP woes, tons of you screamed about hardware not functioning and software not working. Although the complaint crops up every time a new OS hits the street, it seems more pronounced this time. And there's a reason: Windows XP, like Windows 2000, runs on the Windows NT kernel and is a true 32-bit operating system. Older versions, including Windows 95, 98, and Millennium, relied on DOS. The difference is dramatic, with much bigger compatibility implications.

But there are things you can do to put this nightmare behind you or, at least, mitigate its impact.

Advice
If you haven't yet upgraded to XP but are thinking about doing so, start with Microsoft's Upgrade Centers. There are two, one for XP Home, the other for XP Professional. Each lets you search the Microsoft Catalog, a listing of some XP-compatible hardware and software, as well as a link to the mammoth, 50MB download Upgrade Advisor, an app that sniffs through your PC and flags any potential hardware or software conflicts. Downloading the Advisor isn't practical if you have only a dial-up connection to the Net, but some computer resellers carry free Upgrade Advisor CDs.

Hardware
If you've already installed XP, you need a different plan of attack--it's too late for the proactive approach. Start first with Windows Update, the Microsoft service that examines your PC for any out-of-date components, then recommends OS updates and patches.

Although Windows Update may suggest driver updates for your hardware, you should take these recommendations with a grain of salt. We've seen Windows recommend out-of-date drivers, and worse, unnecessary changes to drivers that worked just fine. Instead of downloading updates willy-nilly, visit the manufacturer Web sites for your PC and its internal components, particularly the video card, to see if any XP updates are available. Do the same for external hardware, such as printers, scanners, digital cameras, mice, and the like. To save yourself some time, use one of the Web's many collections of up-to-date drivers, such as Download.com's Drivers section, Drivers Planet, and WinDrivers.

Some hardware, however, may never work properly under XP. We've heard tales of woe from several readers who had to give up their old printers or couldn't get their scanners to work. But don't throw in the towel quite yet. As a last-ditch effort, hunt for drivers that are specific to Windows 2000, which, being an older OS, is more likely to have revised drivers. Windows 2000 is a close cousin to XP, so a 2000 driver may do the trick.

Software
Incompatible software presents an even bigger bugaboo. Some apps, particularly antivirus and system maintenance suites made for earlier Windows editions, such as Norton SystemWorks, simply won't work with XP. You must upgrade. Naturally, you'll want to check with the program's maker for available updates--free or otherwise--to make that old hoss hum in XP. But if you can't find an update, try the following tricks.

If you're having trouble with a specific app, fire up XP's Program Compatibility Wizard, part of XP's Help and Support Center. After the wizard scans your system, pick the balky program from the list, then choose an OS compatibility mode, basically, a setting that emulates a prior version of Windows. If you don't know which version of Windows the software requires, we suggest you try Windows 98/Me first, and if that doesn't solve the problem, try the Windows 95 mode. To skip the wizard for a particular piece of incompatible software, right-click the program's executable file from within Windows Explorer, then choose Properties. Click the Compatibility tab, check the "Run this program in compatibility mode for:" box, and choose the OS from the drop-down menu. You can also monkey with the Display Settings options; some old programs want to work in 256-color mode, for instance. To finish, click OK.

You may even be able to trick older DOS programs, which will most likely be ancient games that you still enjoy, by exploiting XP's Memory setting. Many older DOS games use the Expanded Memory Specification (EMS), which XP does not support by default. Right-click the executable file, choose Properties, then click the Memory tab. Under Expanded Memory, choose Auto from the drop-down list. If that doesn't work, you may need to try other EMS settings or dig out the DOS program's documentation to see if it says anything about memory settings.

For more help with XP's compatibility settings and to hear from real users' experiences in getting their prehistoric programs to work under XP, check out the Web's best resource: Windows XP Software Compatibility Site (not affiliated with Microsoft). Others may have already solved your problem.