Screen Crashes with games and browsers

[Guest]

Hello,
For quite a while now, (i've put this off as I am thinking about a new computer when I move house) my computer has had this problem that I can't quite seem to put my finger on. When doing things partially graphically intensive with my computer the screen crashes. Now, it's not just a regular frozen screen/black screen and then a reboot. The screen looks as if every pixel has been shifted to the side and there is pink and green pixels scattered over the image, weirdly the sound plays in the background but only a repeated 3 seconds or so. For example, when loading Left 4 Dead it freezes on the Valve intro and makes the constant bass note over and over again. The same thing also happens when I try and use Google chrome (without the Valve noises of course)

I have checked the specs of my computer and they are of an adequate state to run such games and browsers.

AMD Athlon(tm) II X2 240 processor
2.8GHz 2.00 GB RAM

Display
NVIDIA GeForce 7900 GS
256MB

So far this crash has occurred with:
Google Chrome (after using for around 10 mins)
Left 4 Dead (Loading Screen)
Age of Empires III (Loading Screen)
Minecraft (If I put it into full screen)
ARMA II (Loading Screen)

Sometimes there is an automatic restart made, others it just stays on the crashed screen and I need to force a shut down by holding the power button.

Any help would be appreciated because if this is a minor issue it may save me a couple of hundred pounds. Thanks.

 

[trapper]

I'm guessing it's either the GPU or PSU. If you have a spare PSU around that you can test with that would be an easy way to exclude the PSU as a problem, or determine that it is the problem. To check the GPU watch it's temps as you open one of these games.