Loud static noise and freezing.

[Gawfo]

Hi everyone, I hope i'm posting in the right place. I joined this forum because i need some help. Less then a week ago i purchased a new sony laptop model number sve151a11w. My problem is almost every time i play a game (i only have dawn of war 2 + expansions and minecraft at the moment) after a couple of minutes of playing there will be a loud static sound from the speakers then the computer will freeze, the only way to unfreeze it is to hold down the power button until it shuts down. Ctrl + Alt + Delete doesn't work, the windows button doesn't work and i'm starting to get worried about shutting my computer off like this all the time.
Any help is appreciated.
Cheers, Ben.