When I first noticed it happening, it didn't matter whether it was running off the battery - it would shut off. It turned out to be an issue with corrupt sectors on the hard drive, and running chkdsk brought it to its current state, so it will at least play video when running on outlet power and the crashes when it's not plugged in are less frequent. I also dusted the insides with a compressed air canister. (Okay, I had the guy at Best Buy do the dusting. I didn't want to break anything.)
I installed HWMonitor, and the idle temp is around 30 C. I've never seen it go above 60 C. I do play some games on this machine (The Sims 2), but I check the temperature frequently (both with HWMonitor and by sticking my hand under it) and I keep my eye out for graphical artifacts. None. So it's not overheating. I know the fans are working because I can hear them running and adjusting for performance. I keep the laptop elevated.
No weird sounds have been coming out of it, although it does often make what I can only describe as a quiet, stuttering sort of grunt. It doesn't sound like a failing hard drive, from what I can tell. Actually, I think it's always made that noise.
I recently replaced the battery, as it was dead.
Edited by Telekill, 28 April 2012 - 08:09 PM.