Graphics card crashes.?

*This is a copy of my previous question, because I had to restart my computer and could not get into the other yahoo account >.<

My graphics card crashes when playing Amnesia: The Dark Descent, my monitor tells me there is no input device, but i can still hear sound and alt+f4 and get a response. I have an ATI hd 4650. I installed rivatuner and I had a maximum temperature of 58 degrees Celsius. I get about 5-10 minutes of gameplay in at this temperature before it crashes. This is the only game it happens to. I tried updating my graphics card drivers but that caused my to be left with a very tiny resolution and gave me 4 bit color. I did have to remove a heatsink off my motherboard in order to install a sound card because the heatsink was just a little too close to the pci slot. The heatsink is back on now, although not secured all the way, and has a new layer of thermal paste.

No, I didn't take the CPU heatsink off, I don't think my computer would be running at all without that. I believe it was the onboard video heatsink. It is covering the entire chip still, I just had to move it not even an inch. And my computer does not crash during any other more graphics intensive games, so I don't think that is the cause. Right now the ATI site gave me the wrong drivers, I'm stuck with 640x480 resolution and 4 bit colors. Once I get this fixed I'm going to try the game again and monitor my motherboards temps.