The upgrade installation is the easiest way to convert an old PC to Windows XP. When you make an upgrade, you install Windows XP on top of your previous version of Windows, and retain access to all your old applications and data.
Before you upgrade to Windows XP, make the effort to download the latest version of all your key hardware drivers. Go to the manufacturer's Web site, or to DriverGuide.com (www.driverguide.com), and grab the Windows XP, Windows 2000, or Windows NT version of all your drivers. (Because XP is based on Windows NT/2000, it uses those drivers—not the drivers used in Windows 9X/Me.) Store these drivers in a handy folder on your hard drive, in case you need to install those drivers post-installation.