Laptop overheating to extreme temperatures?

Truthful I have the Toshiba Satellite A665. I got it around a year ago for gaming purpouses lone. 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 win a random shutdown without warning or i get a flash of a random dark blue screen error. The thing is that i used to Be able to run COD: World at War WORK TIME next to end. But close to I said now it can only run for around 30 min. Im getting the same piece on every game i play (Black Ops, Dead Rising 2, Sliver Cell: Conviction) I can only leap about 2 levels and then my computer module do the things i mentioned above. So first i thought it was just windows acting ahead but then i downloaded speedfan and then i saw that correct before my computer would shut down, The GPU got upward to 100c! (About 200 degrees!) and my Cores are at around 95c! I have NEVER cleaned out the dust from my personal. (Afraid opening it would void my warrenty) but i looked under my laptop upright and everything was covered within a layer of dust. I was just curious if that would most likley be the problem. I already schedualed a cleaning of my machine insides and cleaning of my laptop heatsink on monday. Like i said, I person only had this since the finish of last summer therefore im hoping thats the hang-up.