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.

 

[Solari]

How are you sure it's graphics? I found that my Midiman MidiSport was causing my computer to freeze, not my video drivers. What USB devices do you have plugged in?

Are you getting blue screens? How are your temps?

 

[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.

 

[reflux]

Could be the PSU.

 

[biron_w]

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

 

[reflux]

Aye, but it's not what I would call a trustworthy brand. Have you got another PSU you can test with?

Also from my time with a P5N-E SLi, you need to make sure the northbridge and southbridge are getting adequate cooling.

 

[PaulyD]

overclocked?

Run stress tests on cpu (prime small and blend), does it do it with furmark as well?

 

[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?

 

[bosTRom]

Have you inspected fan/heatsink on card to see if its clogged with dust as well? If so blow out gently with tinned compressed air.

 

[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.