I've had the same problem recently and i noticed that my laptop was getting very hot. It just kept switching itself off and I really had no idea why. I spoke to a man in an internet cafe and he suggested a laptop cooling pad which I bought and hey ho, no more problems. It has 3 small fans in it and I paid 29.99 for it. I leave my laptop on all day and it no longer gets hot and more importantly never switches itself off. Worth a try I guess. Hope you solve the problem.
Paul Wagstaffe, June 2007