My pc always reboots at end of mission 1 (when the car goes in water after heli attack)

I had the same crash issue with my PC. I just discovered my NVIDIA card was not ramping up the fan speed on the GPU block. This was causing my system to crash.

I have an Asus GTX660-TI, and Asus has a tweak program. The fan was on auto, I put it at 100% since it never seemed to go higher than 10%. I also noticed using the video card monitor, that my card is running at 100% during game play!

At 100% fan speed my Video GPU temp was 51C. Give it a try. Holding my GPU temp down cured my crash problems.