PC shuts down when playing games

[DarkCrusade]

Hi guys, I have an issue with my PC and cannot fix it on my own, and I am no expert in that topic, so I'm asking you guys to help me out. It is really annoying, because I do not play a lot, but when I do, my PC keeps shutting down without saving my new saved games.

I have had no problems with my PC until now, so I guess that it has to do with damaged computer parts or something along the lines, but I cannot put a finger on it. The situation is as follows: I start a game and most of the time, it works for around 20 or 30 minutes. The PC will shut down entirely without logging off or saving any new data.

My computer specs:

OS: Windows XP Home Edition SP3 Build 2600
Graphics: Radeon X1600/X1650 Series + a secondary
Processor: AMD Athlon 64 X2 Dual Core Processor 3800+

Real space: 2GB
Virtual space: 2GB

The only thing I have installed in the past month is the game "Risen" which I am most unhappy to have shut down due to the progress being lost whenever my PC crashes. Any help is appreciated! Surfing the internet or running other stuff like iTunes works like a charm for hours and hours.

EDIT: It appears that my PC is overheating and therefore shutting down. What can I do against this issue?

EDIT2: I downloaded HWMonitor and the information I could gather from looking at the stats proves my earlier assumption of overheating as the cause for the shutdowns wrong. The fans are working at around 2400 rounds/min and my processor's temperature is at 55° which is great from what I read in some forum. Something that caught my interest, though, are the voltages. Now, I do not understand too much of this stuff, but my power supply only has 400 watt. Could it possibly be that there is too little voltage for all the components?

[GhostRiderSwiss]

answer to edit1 : better ventilation system could propably solve it already.
answer to edit2 : 400 watt seems actualy to be a bit less but when you would have too less or too much the pc shouldnt work.... so i think its the first problem...

Maybe consider to get a specialist as it always can be something realy dumb and simple which someone wouldnt figure out without looking at your computer :/

Also, if you didnt try it yet, try to run the game with lower graphic as it propably wont overheat that quick....

No more ideas 

[L[0ne]R]

400w is really not a lot, so it could be a problem. Try unplugging any unnecessary devices like DVD-ROM, external drives, any unused internal hard-drives, and everything else you don't need to run games. Then try playing and see if it makes any difference.

[DarkCrusade]

I figured it was the ventilation. I took my PC's cover off, removed all the hair and dust that was in there and noticed that my PC was stuck in a bad position where it would blow the hot air it emitted back in, so no wonder my PC had that issue. Everything is fine now and running

I am already playing Risen at the lowest possible graphics settings and the game lags sometimes. Maybe I really need a new power supply even though the crashes are solved..

Thanks for the answers!