well since you have integrated graphix you can rule out the problem of an overheating video card. and since it only happens when you "do" or "open" certain things it may not be overheating but a problem else where.
i would recomend you get some software so that you can check the temps of your hardware. and get back to us on what temps ur getting. "speedfan" is a good one and its free.
also laptops tend to get really hot because of the how close everything is and the battery usually heats up to a good temp after a couiple hours so theres a couple things that could be causing your computer to stutter and shut down.
my guess is that its your hard drive, but get back with those temps and that will help people to narrow down your problem.