I have an HP Pavilion dv9000 laptop that's gone through two previous owners before it was mine, so it's a bit old. I've never had much trouble with it except for this. The computer crashed without any warning or error message, just completely shut down. I tried to boot it back up but it would get as far as the black screen with the HP logo and then crash again. It took me several tries to get it running again, and when I did, it worked for another hour or so before crashing a second time in exactly the same way, and then again a third time another hour or so later. It booted up fine after that and hasn't given me any trouble since, but I'm trying to figure out what happened so I can prevent it happening again. I tried running a full virus scan but turned nothing up. I haven't done anything unusual with my computer recently except that I hadn't used it in almost a week (I normally use it almost every day).
Any ideas on why this happened or what I can do to keep it from happening again?