Homebuilt Problem

Hi i built a computer few weeks ago , but every time when i play a current game like Guild Wars 2 ( and many others ) my computer crash after 30 minutes. There is a lot of color then it crash
The fact is that there is no freeze during the half hour , the computer can easily handle the game , i don't know what's the problem

My config :
Motherboard : ASUS P8Z77 Deluxe
Ram : Corsaire Vengeance 1866 Mhz 4x4 Go
Graphic card : Nvdia GeForce Gtx 570
CPU : I7 3770 k
SSD 128 Go ( Windows 7 - 64bit Installed )
HDD : Seagate 1To , 7 200 rpm , 32mo


Thanks for helping.
Khel