Could be the RAM, run memtest. Could be HDD, run CHKDSK.
I doubt it's the motherboard though, if it was the mobo then I think you would've gotten more serious problems than just freezing. Have you run any kind of stress program on your current 8800GT? Update the driver aswell, just to make sure that it's not that. What's your temps on your CPU and GPU btw?

I doubt it's the motherboard though, if it was the mobo then I think you would've gotten more serious problems than just freezing. Have you run any kind of stress program on your current 8800GT? Update the driver aswell, just to make sure that it's not that. What's your temps on your CPU and GPU btw?