My Acer keeps black screening!

Hello,
I have a problem with my Acer 5535 it has an AMD Turion 2ghz dual core processor, and everytime i use it, after a while it just black screens and dies, sometimes takes 10 minutes, sometimes lasts for as long as an hour, but it seems to do it everytime, it doesnt seem to be getting too hot, was wondering if anybody had any ideas? thanks :)