Graphics card making computer freeze?

[biron_w]

I seem to be having problems with my graphics,when I try to play games it has a habit of making my pc freeze so I have to reset it.I can't see any reason why this should be.
Specs for pc are:
Asus P5N-E SLI motherboard
intel q6600 quad core
PowerColor ATI Radeon HD 3870 X2
Hi-Power Black 800W 14cm Blue LED Fan PSU
4GB corsair DDR2 800MHz/PC2-6400 XMS2
Running vista 64 bit
Got 2 DVD drives and 3 hard drives.
Just wondering if anybody can figure out what's going wrong.

 

[biron_w]

I assumed it's the graphics card as it only freezes when I try to play a game.
Get no blue screen.Temps are fine.
USB devices are my mouse,keyboard and a webcam.

 

[biron_w]

PSU was bought especially for the graphics card.I assumed 800w would be enough.

 

[biron_w]

Looks like it was just because the resolution was set too high.Even though I only had it set on recommended settings.Seems to working fine now.

 

[biron_w]

Turns out it wasn't because of the resolution as it still does it.Should I try increasing the fan speed of the GPU?

 

[biron_w]

I had a look at it all the other day to make sure there wasn't any obstructions and it's all fine.
Might try putting the fan speed to 100% when playing games and see if that helps.