Problem with pc (rebooting when gaming)

[Allin]

I have bought a second hand bequiet bqt es 600w psu and a Gainward gtx 550ti and it worked perfectly 2 months and now after i start a game the computer is rebooting.
I have a phenom 2 x6 1035T cpu and 4gb ram
Before the reboot the screen looks like in picture http://s9.postimg.org/wvn69fl3z/20150305_160301.jpg

Please help!

 

[cin19]

The problem may from the GPU or PSU.
Like that , if the PSU does not provide enough power to the GPU, it will act like that. Or the GPU is going to die.
If you have other PSU or GPU to test, and you will be easy to know which has problem.
Also make the cpu or GPU temp are ok too, using the hwmonitor to check out the temp.
Hwmonitor http://www.cpuid.com/softwares/hwmonitor.html