Windows XP SP2 keeps Rebooting - Please Help

Hi,

I installed Windows XP SP2 (Home - OEM -
Full Edition) and a PC and it has been working fine for a few months. We had
family visit over the weekend and now, what happens is that the computer
keeps rebooting during the time the Windows XP is loading. I've tried Safe
mode, Last known Good Config, Normal Mode, Command Prompt, booting from the
CD, etc. And for each way, at some point during the loading of XP, the
computer just reboots.

I'm fairly familiar with how to fix many PC problems, however I can't get to
any point where I can try anything.

Any help?

Thanks
Garrett