When you reinstall XP, make sure during the setup (while you're still at the blue text screens) that you delete your current partition and re-create a new one. Once you've done that, do the full format (rather than quick).
Before beginning, make sure your BIOS settings are correct - change the option for 'Plug n' Play OS' to NO.
If the issue continues, remove any sound cards, modems or other extra devices. Once you've installed Windows XP, add the devices back one at a time.
If you think there maybe an issue with the hdd, go to the manufacturers website and download the diagnostics app to test it out (usually under support > downloads).
Good luck.