Once you upgrade your XP installation to Service Pack 3, Windows won't ever allow you to install an older version (including earlier editions of XP) without either wiping the hard drive clean or installing to a different drive. Even if you do install "fresh," you'll still have to then endure a separate SP3 upgrade. The solution is to create a new hybrid installation disc from whatever installer CD you have and a special version of SP3, using a process known as slipstreaming

To prepare a recovery CD, you'll need only three things: a Windows XP install CD (any edition), a valid Windows product key, and about 1.5 gigabytes of free space on your hard drive

The install CD can be any version, including Service Pack 2, Service Pack 1, or the original release from 2001.