Windows 7: GTA IV crash

Yeah I think the game is just stressing the cpu a lot,you could add new thermal paste to see if it does anything or get a new heatsink that provides better cooling.

I had a gaming rig cut out on me several times under heavy load, after checking the graphics card, RAM and CPU it turned out to be a failing PSU fan.

The heat was not being removed quickly enough thus the PSU overheated and the system shut down. You might want to add the PSU fan to the list of things you check are working properly.