I've had stop errors on and off for a few months now and I've never really known the cause of them. I've ran scandisk /f /r several times and also done that RAM check which has come back clean every time. This morning my comp restarted without warning, I ran defrag once it came back up and let it run through the night. Well apparently it restarted again only 1.5 hours later. Here are both minidumps, I run Windows XP SP2.