Temperature issues can definitely be a problem, and you would not be the first person to have the problem you describe be caused by heat. After doing some searching, Speed Fan
looks like it would be a good piece of software for monitoring the temperature of the GPU, CPU, and hard drive. If heat is the problem we might be able to help you find a fan or other cooling device for whatever it is that is getting hot. Anythings getting hot can potentially cause the shut down.