Well they started as Dell Dimension E510's. I told my husband if we upgraded anything else all we'll have left is the Dell casings. We have 2 Dell Dimension E510's that we've upgraded over the course of the past 4-5 years.

Don't know if it's significant to the problem or not but both have received the following upgrades:

550watt power supplies
Nvidia Gforce 9600, 512 DDR3 graphics cards
Samsung CDRW/DVD drives
And 4 sticks of 1gb DDR2 RAM (though window xp only registers 3.25gb of ram)

And all was going well. It was just after the 1st of the year that the new 2gbs of RAM was added to make the 4 gb total.

Only recently 1 of the computers (his) decided to sputter in the game we play. Little mini freezes and lag, into a full blown lock up. It shut the game down, a loud beep emanated from within the tower and the entire system shut down. Didn't restart just shut down.

He said it was showing the general signs of over heating. So he took apart both computers to compare temps and to check to see if all fans and what have you were working. Replaces the thermal compound in both. (as our luck goes 1 computer breaks 1 week later the other has the same problem as their identical) So he did mine too. Mines running great better than it was before he applied the artic silver 5 to them. His however is still having the issue.

For the past 3 days he's gone through diagnostics and every form of system test he can think of. Removing the ram, setting a fan next to the open case, replacing the graphics card with the old one, putting the old ram back in. Nothing. It's not just on the game, but with everything. Every ten minutes of the computer being on, a beep will sound and the system will shut down. Dell's techincal support isn't being much help as the warrenties expired as these computers are at least 5 years old. We're at a lose.

So long post short. What are we missing or over looking? Because both computers are exactly the same inside as far as hardware goes, it's kind of perplexing as far as what went wrong. Both were upgraded the same, nothing was set up differently, yet the 1 won't work past 10 minutes with out shutting down.

Any insight would be helpful, as to what we should be looking for. Thanks in advance :D

Oh yea.. the computer is virus and spyware free. Both scans with Avira AntiVir Personal and Malwarebyes came back void of any malicious files and content.

I would have suspected a thermal issue too. However, if thermal compound did not resolve the issue, the failure is most likely a defective cap.

WARNING: Capacitors may retain a charge long after power is removed from a circuit; this charge can cause dangerous or even potentially fatal shocks or damage connected equipment. For example, even a seemingly innocuous device such as a disposable camera flash unit powered by a 1.5 volt AA battery contains a capacitor which may be charged to over 300 volts. This is easily capable of delivering a shock. Capacitors may also have built-in discharge resistors to dissipate stored energy to a safe level within a few seconds after power is removed. High-voltage capacitors are stored with the terminals shorted, as protection from potentially dangerous voltages due to dielectric absorption.

The tops of 'healthy' caps. Will be flat. Those which are failure prone will have rounded tops. A picture of a healthy cap. May be found here:
Capacitor - Wikipedia, the free encyclopedia

I would first look around the processor. There should be about 7 yellow colored caps. To look at. Next check the 18 or so black caps. Centrally located on the motherboard.

http://www.redplanettrading.com/ebay...203/top800.jpg

If any of them have rounded tops, you've probably found your culprit.