I have two Windows 7 machines, both with Windows Update set to "ask me before downloading or installing." Occasionally (about twice in two months so far), the machines seem to reboot themselves when I'm not around. This happened both times overnight. (Both are on a corporate network.)
What I would like to do is somehow determine the reason, and/or time of the reboot. For example, I can see that Windows Update did not install anything since November, so I know that it can't be that.