I have a Toshiba Satellite running XP
I was using it when I saw the battery light was on and when I went to check to make sure the plug was in it shut down before I touched anything. (I don't think the problem is a poor connection)
I started it up to a black screen that said it stopped responding , restarted unexpectedly or was automatically shut down. It gives me the option of starting in safe mode, in safe mode with networking, in safe mode with command prompt, starting normally, or using the last good configuration.
If I choose "normally" or "last configuration" it starts windows then the power cuts out and it restarts the computer again going to the same screen. If I safe mode in scrolls through some files but the power cuts off again.
I'm not sure if this is relevant but this computer hasn't been connected to the internet in 6 years or so. But the AT&T person who came to hook up the internet plugged it into this computer while I was out of the room. I came back and it seemed to only be on the Google Homepage. I immediately unconnected it. I'm not sure if it was able to catch a virus in that time. The security updates are several years old. And this happened a day or two later.