Computer Freezing After Exiting Games?

My system is a Toshiba laptop p850-05[CODE]Ever since i bought this laptop, it has been running desktop applications very fine for countless hours, but when it comes to gaming, I have had all sorts of troubles, the main problem being :1. The whole system freezes (video lock-up, nothing to do but hold power button for a hard reset) shortly after exiting games that I have played for 30mins to 2-3 hours. I can use the desktop for 0-45 seconds before the freeze happens. It mostly happens after exiting games like Diablo3 or Heroes VI.2. In other cases, in games like Skyrim or Max Payne 3, the freeze happens in-game. Max Payne freezes during the cutscenes (which often the video becomes out of sync with the audio). Skyrim freezes have been random. I initially suspected GPU overheating, but after running a series of tests like a video card stress test that ran without a freeze for hours, playing the games with the lowest gfx settings, I've concluded that overheating wasn't causing the freezes.

All my video card drivers are up to date as well as the bios.I contacted Toshiba tech support to be answered by, excuse my lack of respect here, total idiots who didn't know the first thing about computers (ie, claiming a GeForce 7800 was so much better than the GeForce GT 630M just because of the higher number). Aslo their ultimate conclusion (after speaking to senior tech support) was that I shouldn't be playing those games on my pc because it is not good enough!