Basically, whether it be after 5 seconds or 5 minutes, during the games the screen freezes and displays any number of different colours or shapes. An image of a recent crash has been enclosed with this post to aid you in your diagnosis. It doesn't always look the same as this, just similiar. Sometimes only 10% of the screen will go, and sometimes it takes the shape of the car only; it's very varied.
My graphics card I believe is a Nvidia Geforce 7600GT. Im aware that's it's a little old, but It plays the games very nicely at the levels I have it set at, up until when it crashes.
When i check the temperature of the GPU in the control centre, it idles at around 48-49 degrees C. during the game, the max I've seen it reach as around 70. However, just before the most recent crash it was only at arond 50 degrees, so i don't think it's temp related. However, I have no technical knowledge so I'm only making assumptions. my comp has a gig of ram and a 2.80Ghz processor.
Any ideas? Thanks.