pc crashes when running a game

[daviebhoy]

I have just built a new system, the specs are in my sig
The problem is any time I try to run a game after about 5 min I start to get artifacts on the screen then the pc crashes back into windows Vista.
I have turned the gfx card fan up to 100% in rivatuner but it still happens.
The temp never goes above 59 deg c.
It happens in all my games C&C 3, quake wars, far cry, COD4.

please help

 

[daviebhoy]

I'm not overclocking at all, the artifacts appear almost instantly then it crashes.
i've tryed diffrent drivers including beta ones it makes no diffrence.

 

[daviebhoy]

cheers I'll try that now

 

[daviebhoy]

I underclocked it to 600 Mhz for the core and 800 Mhz for the ram and was able to play enemy territory for about 35 min before it crashed.
I think I may have to rma the card.