David,
There are, of course, a number of reasons this can happen. If you haven't
made any other changes lately, and this just kind of started out of the
blue, one thing I can think to try that is relatively easy and cheap is to
replace the motherboard battery. I don't know how familiar you are with
hardware, but connected to the motherboard there is a small lithium battery
which is usually a 3V battery. It is easy to replace, and not too
expensvie. This, by no means, is the only thing that can cause this sort
of behavior, but when one of my machine started randomly rebooting, I would
also notice small BIOS changes, like all of the sudden the on-board LAN
would be detected when I had explicitly turned it off in the BIOS.
One other thing to mention, if you are running XP, you can sometimes see the
blue screen of death which appears before the reboot. You have to go into
your system settings, choose the advanced tab, then click the "Startup and
Recovery" button. In there there is a check box which automatically causes
the system to reboot on blue screeen. If you uncheck it, you may be able
to see the blue screen and any messages it contains. You may then be able
to use this information to find a more specific idea as to your problem.
Good luck,
Mike
