I usually leave my laptop plugged in. But when I unplug it and let it run off the battery, it will shut down, then start back up to the screen that allows you to start in safe mode or start normally. Even if I am not doing anything on it it will restart, but only if running off the battery. The battery has a good charge so it's not that, but I have no idea what else might be wrong.
I am runnig XP also.
I am runnig XP also.