Computer shuts down after some minutes

[Googolplex]

The only reason I said to try it, is to make sure that the problem is the psu. I don't believe the gpu causes the problem. The power supply cannot support the load. You won't play newer games with such a graphics card. Try any game and see if the problem occurs again.

Edit: 4,444 posts. Too many fours!

But when I reduce graphics quality and resolution, the PC still goes off.
I don't believe that the graphics card load max power when I play on 1280x720 and with low details.

The other phenomenon is, that I can play Amnesia TDD on max graphics without any issues. Some other games also. But most new games not, even Dear Esther kills my PC.