To reformat you stick in the Windows XP disc or any OS disc that is bootable and restart your computer. If it does not come up with a message asking you to boot from disc restart again and press the config key (usually F1 or F2 or F8) and it will come up with a menu using your arrow keys go to the boot tab and set it so your DVD/CD drive is first then save and exit (usually F10) and restart, look for qeustion "Would you like to boot from CD?" or something along thoughs lines.
(Just if you didn't know how to)
