Laptop display problem

Pls help me.. I have a problem in hcl laptop display..while i playing game.my lap disp starts flickering.and goes black.. When i pwr on .. Its starts running..power button lights on..bt no display.. Its fuly black..
I hooked up with external monitor.. No display.. Changed the ram to another slot..
Removed battery.. Pressed the pwr button.. And put it on the battery again and starts..bt no use.. Help me..