computer (Thinkpad X61) shuts down automatically, no warning
 

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.

Check power setting
 

Check Power shutting to see whether it has been set to shut off hard disk and screen at a specific time.
Go to the screen saver page or control panel power options to do that.

Nope, doesn't seem like it. I see nothing in my settings that would indicate it is shutting down at a particular time.

Those temperatures are indeed high. I wouldn't be surprised if the CPU heatsink and/or fan were clogged with dust, unless there is a more obvious problem such as a failed CPU fan.

That's hot. What you're describing sounds like an overtemp shutdown. The fan is probably dirty or not turning properly. I've had to replace one once--a real pain.

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