Hey everyone. I'm not writing to support because this isn't strictly a GoG related problem, and it's a problem that's really got me scratching my head. Unfortunately, I can't play any games until I resolve it so hopefully one of you guys can help me.
It only happens when I'm playing video games. The computer will shut off without warning; no fragmenting, artifacting etc...it's as if I just pulled the plug on the computer. I originally figured my power supply was going bad so I replaced it with a new one, but the problem persists. This isn't a new system, I've had it for a year and this problem only started a few weeks ago. Any ideas?
8800 gts 512mg
2046 RAM
Intel Core 2 Duo 3gigs
WinXP serice pack 2

It sounds like your graphics card is overheating when playing games and therefore the computer will shut down in order to avoid damage.
Maybe you should first run a program which monitors the temperatures of the system's components. I only know SpeedFan for this, but there are probably more suitable ones. Or just feel how hot your graphics card is when the system shuts down the next time. Though, you probably better turn off the computer's power before doing the later ;)

Not necessarily graphics card, I had a similar problem with CPU - yeah, it wasn't properly installed, but still, problem began to occur after maybe year.
And try to run anti-virus software. My experience as well :D

Speedfan is the quickest imo, I use it too. If you find one temp over 60/70 at idle well... this ain't good :P
I also know that a bunch of nVIDIA 8800 were overheating. This might be your problem, yep.

Hmm...lets see...
I suspected a gfx problem to begin with but dismissed it due to a lack of fragmenting and artifacting that normally accompany an overheating gfx. But, I do happen to have a new heatsink laying around that will fit my gfx card so I'll give that a go.
A CPU problem hadn't occured to me, again from the lack of artifacting or an overheating error message. But I suppose it wouldn't hurt to apply some new artic paste to it anyway.
I'll try everything out and keep you updated, thanks for answering!

About the CPU... try SuperPI to benchmark it. It works very well :>

erm 100 celsius is 212 fahrenheit.

Oh man here we go, the only problem with Speedfan is that is sometimes misreads the informations. You clearly have a heat problem, and it seems coming from the CPU. Come on... E8400?
I have one as well and the temp captor is kinda fucked up, it doesn't get the actual temperature but a badly calibrated one. Maybe yours is so wrongly calibrated that the BIOS think it's too hot and shut down the computer.
The best way to verify it is to open the computer right after it was shut down and "feel" the heat coming from the CPU.
You americans are the only one using this "thing" :P

right....so that's too hot is what you're saying? And 'temp 1' is what indicates the temp of the gfx?

''Oh man here we go, the only problem with Speedfan is that is sometimes misreads the informations. You clearly have a heat problem, and it seems coming from the CPU. Come on... E8400?'''
My processor? It's a E6850. Why do you assume it is a CPU problem? The last time my CPU was overheating (a different system), the comp would give me an overheat message.

212 Fahrenheit is the general operating temperature of most of the vehicles on the road today. If your GPU is running as hot as a CAR, according to the software that monitors your temp, then that to me seems to be the problem...You got a spare vid card laying around whose temperature you can measure and see if there's any difference???

I'm not sure if I'm reading speedfan correctly (I don't know why 'GPU' and 'Temp 1' are seperate).
Unfortunetly I don't have any free graphics cards laying around. However I do have a heatsink I can attach to my GFX so I'm gonna try that. Actually reminds me, that the reason I bought that heatsink in the first place is because the fan on it was making a weird clicking sound when I bought it a year ago, but the sound stopped before the heatsink arrived so I didnt install it.

That clicking sound was probably the bearing letting you know that it's on its way out. Good luck with the heatsink installation. Don't forget to use the thermal paste LOL.
Also, I'm not an expert on speedfan but perhaps Temp 1 is the overall temperature of the video card while the other heading (GPU) is strictly tied to the actual GPU. Is there a readme you could consult on the matter??

A mate of mine had a similar problem with an 8800 card. That was caused by the extra power plug (directly from the PSU to the GFX card) not being plugged in correctly. Don't know if that's the case though.