And when I say "shutdown" I don't mean the Windows XP normal shutdown routine. I mean I get a black screen and the computer is off.

At first I thought this was an overheating issue. I downloaded a program to monitor the CPU temp and it looks like I'm normally in the 70s (celsius) but can get up to 80s. So maybe there is something to the overheating problem.

I've taken out the battery (connecting directly to A/C power) and have positioned the laptop in a way where it, I think, can get a bit more circulation (the back is raised a bit off my desk).

Does this sound like an overheating issue to you folks? I downloaded the latest BIOS and installed that as well. We'll see if that helps.