A reboot after a shutdown is usually a sign that you have a bluescreen when calling the shutdown. I would suggest you to disable automatic reboot on blue screen. By doing this, you'll notice if your problem comes from a bad driver. In order to disable the automatic reboot just follow these steps : 1 - Right-Click my computer 2 - Click Properties 3 - Click Advanced tab 4 - Then click Parameters in the Startup and Recovery section. 5 - Uncheck Automatic Restart in the System Failure section. If the reboot comes from a bluescreen during your shutdown, you'll be in order to find which driver file cause problems. If you can't get no useful information from your bluescreen, check your system's memory and HDD.