What is wrong with my laptop? Help, please!?

I have a Fujitsu N3530 laptop, its three years old. I've taken it to be repaired twice, once for a fan replacement and once to fix the screen imaging. Right now it has a very different problem. I'll be on it for 5-10 minutes, then a screech and a sound like a fuse popping and it goes black. The power on is still on, the disk drive still opens and closes, but the screen has no image and the only thing I can do is shut it off by holding down the power on. It takes an hour or two for it to restart ok. I receive no error messages, not even a warning against the improper shutdown when rebooting. What's wrong with it?