Laptop overheating to extreme temperatures?

So I have the Toshiba Satellite A665. I got it about a year ago for gaming purpouses only. It runs highly graphical games preatty amazingly for a laptop that was under 1000$. The problem is that now I can only run games for about 30 min now and then i would either get a random shutdown without warning or i get a flash of a random blue screen error. The thing is that i used to be able to run COD: World at War HOURS on end. But like I said now it can only run for about 30 min. Im getting the same thing on every game i play (Black ops, Dead Rising 2, Splinter Cell: Conviction) I can only play about 2 levels and then my computer will do the things i mentioned above. So first i thought it was just windows acting up but then i downloaded speedfan and then i saw that right before my computer would shut down, The GPU got up to 100c! (About 200 degrees!) and my Cores are at around 95c! I have NEVER cleaned out the dust from my computer. (Afraid opening it would void my warrenty) but i looked under my laptop keyboard and everything was covered in a layer of dust. I was just wondering if that would most likley be the problem. I already schedualed a cleaning of my computer insides and cleaning of my laptop heatsink on monday. Like i said, I have only had this since the end of last summer so im hoping thats the problem.