1. Disable Automatic Restart. From the Windows Advanced Options menu, use the up/down arrow keys to select the "Disable automatic restart on system failure" and hit Enter.
Hopefully the machine will stop on a Blue Screen of Death (BSOD). Record and post back with the "exact" error message text and/or numbers plus any offending software module it might name.
2. Windows Advanced Options Menu. Use the F8 function key during system startup to access the Windows Advanced Options menu. Tap the F8 key once or twice per second as you startup the computer (or immediately after POST completes and screen flashes black prior to displaying Windows XP logo with its processing bar display).