Windows XP on reboot loop, F8 doesn't work. How can I fix this?

So basically, I did a system restore/re-installed windows XP from a disk. It all went smoothly, until I noticed it would restart after the splash screen. Over, and over, and over again. I tried F8 and tried logging into all 3 different safety modes only to get some stupid error, then rebooting the computer back into the same wretched loop. I went back into F8 and tried system restore, and got another error. Once again, reboot loop. Went back into F8 again and tried looking for "Disable automatic restart on system failure", only to find a blank space where it's supposed to be. I'm afraid to put the disk back in and to redo the OS re-install because I'm worried it might make my computer even more buggy and broken. What do I do?