Ok, my suggestion for the original poster is that if the issue is still not resolved, and you want to know for sure whether it is software or hardware related, reinstall Windows XP. I'm certain that this is a more time effective way compared to 3 months of trouble shooting on a forum with hundres of people suggesting to use software's such as registry fixes which will only worsen problem in most cases.
If the issue persists after re-install, take out all hardware devices disconnect DVD player, CD writer, sound, LAN, additional hard drives, everything that can be disconnected) (Except for 1 memory module, the CPU & graphics card if not onboard)
See how the system runs.
If the same problem occurs the issue is not with any of the devices which you took out, report back to the forum and you can start diagnosing the remaining components (ie try another graphics card/memory module/cpu/hdd if possible).
If the issue was resolved than it was software related and the issue is resolved.
Another option if you wish to go for Microsofts suspected heat issue is purchase another PC tower with good cooling fans/sinks.
As for the last person to post the 0x00190203, 0x839D72A8, 0xc0000102, 0x00000000 error message.
This is a problem with either the hard drive (Bad clusters perhaps) or corrupted files on the hard drive.
To resolve try one of the 2 options:
A: grab your Windows installation CD and boot the CD as per this website's instructions: https://www.wikihow.com/Use-Windows-Recovery-Console-from-XP-CD
B: If you can boot into windows follow these instructions: http://www.updatexp.com/windows-xp-chkdsk.html