Puzzling problem - powerdowns

[Simaril]

Trying to get back to AH, but running into no end of problems. Now beginning to wonder if it might be time for a rebuild.

Long story short - I've got a P5WDH Deluxe socket 775 ASUS mobo, and Core2Duo 6600 at 2.4GhZ with 2GB Crucial DDR2-800 RAM. PS 550W, Radeon X1900 vid card. Running XP pro. Drivers and all are fully updated.

It's done just fine for the last two years with my daughter mostly playing Facebook games. But when I started gearing up for AH, the machine has been acting weird. Apparently, the onboard audio drivers got corrupted somewhere along the line, and when I started offline AH I got system hardlocks that could only be interrupted by holding the power button down. This happened about a dozen times before we diagnosed the trouble and got the drivers reinstalled. I'm worried that there may have been some damage done by those manual over ride shut downs, because strange things are happening since then.

Most concerningly, the machine will randomly shut off. No warning - just WHAM and everything's black. Weirdly, when I try to power it back up the button will sometimes not work at all. The system will ignore everything until I unplug it briefly and plug it back in. After that, the power button works fine.

First thought was a heat issue, but not panning out. Temperature sensors for MoBo and CPU are OK. Don't have one for the Vid card... Also, the unplug fix works regardless of how long its been since power down - if I unplug/replug immediately, the system comes up. If I wait a long time, the button will not work until I unplug/ replug.

Any thoughts?
Or should I just bag it and get a new MoBo and CPU?

[MonkGF]

Check the power supply.

[Simaril]

Now thinking it's temp after all.

Left my monitoring program running while performing tasks, and all was OK until I ran AH. After a couple minutes, the temp alarm went off.

After shutting down, went to case and found enough dust to build an igloo. At that point, I began telling myself DUH.

 

[Mar]

When I hear about problems with the computer shutting off without warning, I always think temp. My old rig had it so bad I had to keep the cover off while playing AH, course I didn't know much about dusting then either. Heck, I still don't know much of anything.

[Kazaa]

Temp or PSU

[columbus]

temp or PSU and check caps on motherboard.

[Dragon]

I'm leaning towards the PSU.  Dirty fans will pull a bit more amperage, combine that with the VC pulling amps to run AH and it sounds like the PSU is shutting down on a safety limit. 

Cleaning it will help, but I think at least a new PSU is in your near future.

[Eagler]

used one of these on mine last month

Now I have it sitting up on a cinder block - the power supply on the bottom doesn't help.