why would my computer turn off

for some reason my laptop will just shut off after using it for 5 minuets or so and some times longer but i cant figure out whats causing the problem. any suggestions?

 

Sounds to me like a faulty or overheating CPU! have you checked the fan or the battery might be shot!

 

Can you hear a fan? Does it get louder before it shuts off?
If it is running on battery have you plugged it in? If so. does it still shut off after 5 minutes?

 

Is it shutting down completely while your actively using it or is it possibily going into sleep or hibernate mode. Is your display just shutting down?

If your reading something or watching a DVD without at least touching the mouse for awhile its maybe doing one of the above.

 

it does it sometimes just sitting there right after windows boots. i have opened it up and both fans do work. like 5 seconds before the computer freezes and you here the fans speed up, then turns off. i