Restart the computer and boot from the WinXP cd. Install XP on an empty partition of your c: drive. DO NOT DO AN UPGRADE FROM ME! This way after it installs and reboots it will ask you each time which operating system you want to boot with. If you have problems with XP, you can still boot with ME and try to fix it.
I would still have to buy XP Home Edition (I have XP Home Edition Upgrade), would I not? Not that I’m going to get out of this without spending more money, apparently.