Computer freezes under light load.

Question

Iron

My config:
nvidia geforce gtx 460se
st350041 8as scsi disk device
amd athlon tm II x4 645 proc
4gb ram
Problem:
I play different games. Let's say Dishonored, Outlast, Dota2, CS:GO.
Everything is going well, without delays, I record some games through OBS at ultra 60fps stably.
Yesterday the computer for playing cs:go (~40 minutes) hung up three times. It hangs tightly, the sound of the last second is spinning in the speakers, a black screen, the computer is not cut down. Reboot helps - if you don't run csgo - it works completely. There is additional cooling on HD, mother, processor and video card, 5 screws.
What is the problem and how to solve it?

Answer 1

Sounds like an overheated cpu.
Set up a monitoring program and monitor the temperature.
AIDA64 - System stability test

Answer 2

Overheating of the north bridge is also possible, especially if the computer is overclocked.