Random BlackoutsFollow

When I'm using the computer, it'll just randomly black out, stop responding, cut sound, etc. The monitor is still running, just showing a blank screen, and it does not respond to any inputs. I can only get out by a hard shutdown. This happens at seemingly random times (anywhere from 2 minutes to 2 hours) and I haven't made any connection between what I may be doing and when it blacks out.

Additionally, the computer now has random "freeze" moments, where everything takes a sudden stop for 2 to 4 seconds, before resuming. This problem only started after the blackouts started.

I thought it may be a virus and booted the computer in safe mode. I ran a scan with Spybot, Malwarebytes, and Microsoft Security Essentials. I only found a few small things, and took care of them, though the problem still persists. Important to note though, is that the computer didn't black out in safe mode, regardless of how long it was left running or what I did.

I run vista on an unmodified notebook, that has served me very well for over two years. I would greatly appreciate any help that the zam community may offer.

I'm going to have to agree with the person above. Since you are using a notebook its most likely the drivers. But another common reason is if your computer is overheating a lot of notebooks have safety features that will shut the notebook down. If thats your problem try to something that lifts it off the desk, tabletop, your lap, etc so that air can get completely around the notebook. I haven't much luck with the $35-50 fans that go underneath the actually computer.