Get a Linux Live CD and reformat it with that. Once it's wiped install XP.
AMD Athlon 64 3200+ Venice Core, MSI K8N Neo-4, 2x 512 Corsair Dual Channel, Nvidia Geforce fx 6600 256MB, 160GB HardDrive
Windows Vista Business Edition
"There are 10 types of people in the world. Those who know binary and those who don't."