Dell Latitude D520 restarts spontaneously

Question

I have a 2 year old Dell D520. In the last 2 months it is randomly restarting. After hours of calls with Dell support, they claim this is a software issue. Their hardware diagnostics tool marked all hardware components as "good". I also replaced the memory sticks on the box.
I installed a clean OS multiple times (Win 7, Win XP, Ubuntu) and the problem persists. I have one image that was created with a vanilla XP and the recommended Dell drivers. That seemed to work for a short while but had the same issue eventually. Going back to this initial image didn't help.
My main suspicion is heat related failure. But I'm not sure this is it.

Any suggestions for more diagnostics?
Any suggestions to address the heating issue?

Answer 1

Tools for detecting heat problems:

GPU-Z will tell you the temperature of the video card
SpeedFan for the CPU and the hard disk
Active@ Hard Disk Monitor for the hard disk (in addition to SpeedFan)

Answer 2

You could try to use Prime95 to stress test your computer and better identify the problem.

While running this tool, check your temperatures with the tools from the post of harrymc.

If the computer crash and the temperatures are normale, then check next the ram with memtest.

If this test is ok, i would change the psu to isolate the problem. If it shows errors change the ram.

When the error then still exist it could be the mainboard or the cpu. (probably the mainboard, maybe a broken soldering point)

Answer 3

If it's not shutting down the OS, but is instead restarting as it would from a momentary power-cut, then I'd suspect your power-supply.

Dell and a few other manufacturers are often stingy about power supply ratings (you might get one rated for 300W rather than 350W just to save a few dollars), so if you've upgraded or added any hardware (or even if not), the system may be demanding just a little bit more power than the PSU can comfortably manage.

And I can't imagine Dell have a diagnostic for the PSU.