I have a Dell Insprion 1525 running vista. Its only a couple months old, works fine never froze once, runs smoothly except today. I was watching a movie and it just shut down by itself. Not shut down actually, it was like like I held the power button and did a Manuel shut down. Every thing is fine then boom. It did it again about 15 minutes later.

I'm guessing its a software problem? I don't know actually, can anyone give me a diagnosis or what to check for?

If it's a hard power down, I'd guess it's a hardware issue.

First of all, being a laptop, check it for overheating. Aim a hoover at the intake vent and suck all the dust and crap out which may be blocking the heatsink and making it overheat.

Sounds like it's over heating, get some air duster, open it up and clean the fans, if the problem continues to happen invest into one of those cheap 10 dollar usb fans that mount to the bottom of laptops.

Almost certainly overheating. I have the same problem with my Dell Inspiron laptop, and I had to get a little usb fan tray thing. Still gets fucking hot though.

By default you should not require to hardboot your laptop in any case. Over heating is the major player here but please check your Event logs they might shed some light on another ignored problems.

Is there a chance that the battery died or disconnected? Was it connected to power? If you were watching a movie, you might've missed the power notification. If not, it probably overheated.