Step 1:
  • Start --> right-click "Computer" --> Properties
  • On the left side of the system properties window, click Advanced System Settings
  • On the Advanced tab, click the Settings button in the "Startup and Recovery" box towards the bottom.
  • Uncheck the box that says "Automatically Restart"
  • Set the dropdown to Kernel Dump
  • Click OK in all the dialogs to exit out and you'll probably have to restart the system.
  • Next time it craps out on you, it should just hang at a blue screen showing a STOP code. Paste the info from the blue screen in a reply here and we can probably make some progress.
  • If it does not blue screen but just reboots, then it is likely a hardware failure due to overheating or something else very bad.