Microsoft claims that XP can run more Windows or DOS applications, including games, than any prior version of Windows. This assertion actually holds true for most programs, which you can run in one of two ways. First, you can rely on XP's built-in compatibility database, which automatically configures memory, video and other necessary parameters to allow certain known programs to run under XP. If that doesn't work, you can use the Program Compatibility Wizard to configure programs that the compatibility database doesn't know about. Some applications and software types have known problems with XP. Check PC Pitstop for a frequently updated list of problem programs. For example, users reported that most utility and virus-protection programs designed for DOS, Windows 95/98/ME would not run correctly under XP because their driver files differ significantly due to XP's NT-based structure.
The Norton nightmare
Norton SystemWorks users reported the most glaring example of what can happen when software vendors must rebuild products for a new operating system. SystemWorks 2001 just isn't compatible, although Symantec said that a Windows 2000 patch could make it work, and the first release of SystemWorks 2002 conflicted badly, causing fits and starts and even full-blown crashes.
But don't give up on SystemWorks 2002 just yet. Symantec's technical support can help clean up the mess and will ship you a free, new version of the product that works very well, although differently, under XP. It's different because XP keeps a tight rein on itself and locks its system files when running Norton Disk Doctor. This often requires you to restart your PC so that Disk Doctor can run before the entire OS loads up. Norton SpeedDisk and other disk-defragmenting products, such as Executive Software's Diskeeper, also cannot defragment all of the files on the hard drive because of XP's system file locking. You can address potential compatibility woes early by running Microsoft's Windows XP Upgrade Advisor, which is included on the Windows XP installation CD and available for download on Microsoft's site. The Upgrade Advisor sports an online database of applications and hardware information, checks the components of your system, and produces a no-go report if an application or piece of hardware is not currently supported by XP. The software even displays any known remedies, although these ‘fixes’ usually just point you to the Web site of the offending product's manufacturer. Don't rely on Microsoft alone. Check your hardware and software makers' Web sites for specific information -- which will probably be more current than that of Upgrade Advisor.