Doesn't he have a power button?
Mine does.[/offtopic]
Tell him to get into Safe Mode.
Generally, F8 before the windows loading screen. Then restart. That could clean any saved stuff from standby/hibernation.
Does the "preparing to hibernate" screen give him an option to delete what was saved (when the batteries ran out)?
It is, indeed, weird. I can remember something like this happened to me a couple of years ago.