I'm having quite a irritating problem here.
When i play games,the computer just restarts after while.
When im sufing the internet,it doesn't occur.

So i'm thinking if it is the graphics,or the computer is 'working too strong'.

I have played the game before,and it occur to most game,not a single one

I would suspect heat. I recommend that you download & install Speed Fan and then run Prime95. I would set speed fan to log the temps before running the prim95 torture test. You should buy a can of compressed air and clean out all of the fans especially the heatsink fan.