First off. let me explain that Processor speed dont really work like that, For you to increase your Ghz u will have to increase ur FrontSide Bust.. but this is a different story..
Well blacks ops is on to ur Graphic Card.
Combat Arms may be more to your processor...
Are you sure ur processor is over heating , my brother plays games and his Quad Core seems the same as ur Q9300 @ 2.5ghz can hit head of 83 degrees C..
Are you sure it is ur processor or could it be the fact that CA is calling functions Effecting parts of the computer Causing it to shut down for safety
Also if your are sure it is over heating.. There are Liquid Cooling cases.