So recently i have been playing league of legends on the high qualities and after about the second game my computer will randomly black out and shut off. During this process the computer itself is not very hot at all but the ac adapter is quite hot. Any ideas as to why this is happening? 

specs

Alienware M17x

BIOS: Ver A10 1.00

Processor: Intel(R) Core (TM) i7 CPU          Q 740 @ 1.73GHz (8 CPUs)

Memory: 8192 MB RAM