From: Lee on 03/20/2006
okay a while back I had the same problem about the computer just randomly powering off and quitting out on me. Turns out all that was happening was the cpu was overheating and the computer was powering off to protect itself.
The way I solved it was to clean the heat sink over the cpu. I'm not saying this will positively fix your problem, but it worked for me so it's worth a shot. You can't hurt your machine by doing this and it is wise to clean your heat sink often anyway.
To do this first open your machine. The motherboard is the biggest card in your machine with a bunch of other cards sticking out of it.
Your heat sink is a spikey square shaped thing usually made out of aluminum about 2 inches by 2 inches in size. Underneath it is your cpu and the heat sink is designed to displace heat from your cpu so your fans can cool it faster.
The heat sink loses efficiency as dust and debris get caught and entangled int it. It is designed to come off usually by a small release lever along one side. Do not force it, it is designed to come off easily so just take your time.
Once removed from the machine, you can use a vacuum cleaner or a q-tip or something to clean it of debris. I can't advise you to use water because if it's not comlpetely dry, bad things will happen.
Once clean just put it back where you found it. Make sure it's secure and close the box.
I'm not guaranteeing this will solve your problem but it solved mine and is a good habit to do anyway.
Oh and by the way to whoever posted that "you should throw away the machine and get a dell". Big help buddy thanks. I'm sure thats all these nice people needed to hear. Dumbass.