When you installed Windows XP, did the installation go smoothly?
Once, my friend tried installing Windows XP for me while I was at class (he's a Microsoft Fanboi). He kept getting random installation errors, and tried flashing my bios. Jacked my bios, so my computer didn't POST. I waited for ASUS to send a new BIOS chip (while resisting the urge to kill him), and then reinstalled Windows XP. However, I kept getting lots of crashes, and plenty of errors.
After lots of trouble shooting, I narrowed it down to a bad stick of RAM. Took out the offending chip, reinstalled Windows XP, and was good to go.
Edit: Are you trying to install a legal version of XP, or a slipstreamed version? If you installed Service Pack 1, what were the steps you took before you installed it. Maybe you had a conflict during the service pack installation.