Pc crashes when playing Metro:LL! help?

Ok, i built my pc almost a year ago an everything has been fine until I got Metro:last light. I played the game for about 2 hours perfectly on very high settings. Then for an unknown reason it began to cause my pc to go into complete spas mode, making my screen go black with lines and producing a loud beeping noise in my headphones. Then it wouldn't let me do anything and required a restart.

From looking at the temps on both my cpu and gpu everything is below 60C, which is why i am so confused. all drivers are up to date.

So then i decided to play some DayZ which I have played over 200 hours off absolutely fine, now about 10 mins of game play and boom, a crash.

these crashes require me to restart my pc and it is becoming very annoying, i have scoured forums for solutions but mainly people say its overheating, but in my case it inst. So anyone who has had this problem or knows how to fix it please help!

My pc specs:

Phenon II x4 965 (stock cooler, no overclock)

Amd R7850 1gb (no overclock)

Asus M5a97 Mobo

8gb 1600 corsair vengance ram

 

As I say, this has only begun happening since downloading metro: last light.