If it was overheating I would expect it to auto shut off as a fail safe. Freezing during gameplay could be faulty RAM, video drivers, or even an issue with the motherboard. The first thing I'd try is uninstalling the video drivers and installing older stable ones from before you were having this issue. If that doesn't work I'd try swapping our one RAM stick at a time to see if one of them might have a fault. If that doesn't work you can try reinstalling windows. If you have an onboard video video card you can trying putting in a dedicated card with stable drivers. Or if you running a dedicated card you can try taking it out and running onboard video or pop in another video card with stable drivers. It could also be a faulty power supply not sending enough juice to your video card or CPU.
