Have you tried looking at the Event logs? That is where I would start if you aren't getting BSOD. Here is how to get there: Start->Control Panel->Administrative Tools->Event Viewer, if you are using XP you should be able to just click on System or Application and the logs will appear in the right side of the pane. If you are using Vista or 7 you will need to click on 'Windows Logs' then on Applications or System..Look for a red mark to the left side of the "event" that is near the time that the system "froze" or "crashed".. If indeed you are getting a BSOD then look into WhoCrashedit from a google search, install and run the analyser to see what it is saying. Just a another thought, this makes me lean towards a video card or a psu.
Edited by snglnluvnit, 12 February 2012 - 03:45 PM.