Alright, I'm just about ready to pull my hair out here. My pc restarts without warning while playing any 3D intensive games (UT 2004, Rome: TW, etc.). I have also noticed it restart when I run nearly anything that is intensive for my pc (disk defrag, virus scan, memtest).

So here's a list of things I have already done to try to fix the problem:

1. Replaced video card (geforce 4 ti4200) with new one (geforce fx5500)
2. Replaced Ram (512mb) with two brand new sticks totaling 1gb
3. Replaced psu (crappy 230w) with brand new 350w
4. Checked out temp. (cpu is only reading about 36c when pc restarts; don't have sensor on gpu)
5. Cleaned out pc case with air can
6. TURNED OFF the automatic restart option in windows system, but I still don't get a BSOD, PC restarts just the same.
7. Downloaded and tried all of the latest (and some of the not so latest) drivers for my video card.
8. Flashed my mb bios, and updated drivers for about every device I can think of.
9. Reset my pagefile memory in virtual memory
10. And about 50 other things I don't even remember anymore.

*P.S.~ If it is any clue; The problem started after the fan went bad on my ti4200 (card has been replaced since then though).

There has got to be some way to make the madness stop!!!

BTW here are my system specs:

Compaq Presario 6000 series
P4 - 2.4ghz
1gb pc2100 ram
geforce fx5500 256mb

The next time it reboots go into the BIOS and check the processor temp. THe processor fan may be failing. There is also an off chance that the old card overheated and damaged the AGP slot but it sounds more line a heat issue.

Ok. I've checked BIOS, but either it doesn't have a listing for my processor temp, or I don't know where to find it. Also, isn't the processor fan rpm supposed to show somewhere in BIOS?

It should be under Power. If that doesnt work try Motherboard Monitor.
http://www.pcworld.com/downloads/file_description/0,fid,7309,00.asp

Thanks,
Ok, i've checked out temps with Motherboard Monitor at reboot. Only 37c! I might be wrong, but that isn't too hot for the cpu is it? I also wanna mention that this restart doesn't only happen during games but in any hardware intesive program. It recently rebooted on me about 30 minutes into memtest (no errors were found btw), and while I was watching an .avi file.

Geez this is frustrating...I was thinking about upgrading my vid card once again, but I don't wanna shell out the cash if my pc is going on the fritz.

Take the side of the case off and let a fan blow into it. Thats one way of finding out if it is a heat issue. 37* is a very good temp. If its not heat related its probably a driver or hardware failure. Have you looked for errors in Event Viewer? When is the last time you did a clean install of Windows? If you do a clean install and the problem still persists Id say its either a faulty motherboard or bad RAM. When your computer was made there was an epidemic of bad motherboard capacitors with the same symptoms you're having.

Definitely sounds like a thermal problem. You just might want to go through your whole case and reseat all your ram, your processor, all your cards and connectors. Sometimes you get some oxidization on those thousands of contacts that cause an intermittent connection on heating.

Maybe it is heat...

Alright, I did as suggested and ran an open case with a floor fan next to it.

I ran memtest (as this always makes the pc restart) and it went about 3 times as long as it usually does before it restarted.

My cpu never went above 29*, but my case temp jumped up to 50* (this was a 15* jump with a floor fan blasting fresh air into the case!)

Is the case temp normally that much higher than the cpu? And if so, should it get that high with an open case/fan?

Anyway, the open case/fan has some effect in that the pc ran much longer than normal (although it eventually restarted )

So what do you guys think? Is there something else causing a bunch of heat in there, or are these temps normal?