Random Power Loss on Dell XPS 600

Question

System is an XPS 600 running XP Media Center Ed. that was build mainlyfor gaming. I bought the system new from Dell. A couple of days agoafter I booted the PC and went away for a few mins. When I came backit was powered dow. I rebooted it and it has run fine untill todaywhen the same thing happened. I rebooted and started up a game. Twominutes later the power went out (like I had pulled the power cord fromthe back of the machine, no warning). I have rebooted it again and ithas been fine for about an hour now, but I know it's a matter of time. What I have done:Checked all connections that they are tightChecked that the power strip is plugged in snug.Cleaned any dust from the outside of the machineThe machine was opened and vacumed out about 6 months agoIdo not thing it is heat related since it can happen just minutes afterboot up and then not for days. Suggestions or ideas? Any helpappreciated..