Screen+ computer shut down but fan is on.

Hello,

I am a active silkroad player.
Since 1 week I got a problem, every time after I start silkroad the screen goes black after like 10-30min.
I hear that the music stops playing so the game also quits including internet etc. But I still can hear the computer itselfs. At least the Fan is still blowing. I tried it with several games reinstalled games updated drivers cleaned my computer formatted everything and some more. When im online on internet or just in windows it does not have anny problem.

Annyone got a idea about this problem?

Anny responce would be greatly appreciatted!