Game blacks out results in crash and pop up of driver error

Hi

Here is my problem. I play a game for a while then my screen blacks out my game crash and then a little pop up note which say's your nvidea drivers has stopped working. This is what I have done to fix it:

Bought a new power supply which I got today ( Same Problem but it seem the problem takes longer to occurred after it was in my pc )
My GPU temperature gets to a max of 50 - 60 *c
Updated my drivers and even set my time ( black ops 2 fix )
Reinstalled my Windows 7
My Direct X is updated.


I don't know when this started since I had this problem for a few months but here is my PC specs:

Intel Core 2 Duo CPU E7600 @ 3.06GHz
NVIDEA GeForce GTX 550 Ti
4 GB Ram
Onboard Sound and Ethernet
700w PSU

Thank you for your time