Uninstalling Windows XP

My nephew brought me his Compaq to check out because it wouldn't boot all the way. No discs of any kind with it. Tried everything(boot discs, restore discs from another comaq, etc) to get it to boot and couldn't.
Just out of curosity I put my Dell Reinstallation CD in. It formatted the hd and installed my Windows XP. When his Compaq tries to boot it shows the bios. How do I uninstall my Windows XP and leave his bios so I can try something else?

You can't uninstall per se. You can pop the cd in and get it to format the drive and end the install there.

Thanks a lot.