My screen goes black and my computer crashes whenever I open a game

Tarek Saber

Honorable
Jul 13, 2013
8
0
10,510
Hi,
My desktop have the following specs:
-Intel Core i5 3rd gen 3470
-Sapphire 7870 Ghz Edition
-Gigabyte Z77-D3H
-Seagate Barracuda 2TB
-Cooler master 500W non-modular

When I open a game and play couple of minutes, The following is the state of my computer:
-Screen is black but still receiving signal
-All coolers fan for CPU and GPU still running and the case fans are still running
-I hear a "zzzzzz" like sound in my headphones or speakers
-The Power LED is still on and still while CPU LED(one that flashes usually) never lights or flashes
-No matter what I press nothing happens
-The only way I can get the compouter to work again is to turn off PSU or unplug it then plug it and start it normally.

I have all drivers updated.
I tried using both windows 7 and 8 and both showed the exact same problem.
I tried many games like LOL , DOTA 2 , Planetside 2 and world of tanks. The problem occurs whatever game I play but by different frequncies meaning that it happens more often in LOL and sometimes in Dota2.
Any advices or anything to check or want any more information?