Windows XP Reboot Loop


Well my advice is that you have to check your cabeling. Open your old 'can' and disconnect your HDD few times, reboot, check if same repeat until success. Try to find board beeper speaker so you can hear board beeps if any. It could be CPU or RAM as well. So go thru post check.
My best guess is moist on disks cabeling that lead to rusted connectors.