Spazzing out

Okay, so I got this laptop last month. Ever since I got it, ( It is pre-owned ) it has spazzed out. The former owner did say this did happen, but not to this extent.
If I play any download-required or big multiplayer games, in a matter of minutes, the computer will pick a random color, sprawl it all over the screen, freeze up, and make the most annoying BUZZZZZZZZZZZZZZZZ sound.Sometimes, when it's not too hot, it flashes white and has a line with flashing and it makes no sound and all it requires is a simple close and open, although I don't exactly enjoy that either. I think it is a overheating and maybe a graphics card, problem, due to the fact that the laptop gets very hot and some graphics such as shadows that are supposed to be in some games do not show up.
Now though, I played a simple flash game with 8-bit graphics and it took longer, but it still spazzed out. When it does spaz out obviously, I'm forced to restart the computer. I can't hardly do anything with this laptop now. Please help.
 
Sounds like you will have to have it serviced. The thermal pads/thermal compound may need to be replaced... What is the make and model?
 
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