How you can create your own one-click shutdown button for the Windows 8 Start screen.
1. Go to your desktop.
2. Right click and create a new shortcut.
3. Type in the following for a shutdown button:
shutdown /s /t 0
4. If you prefer to use a restart button instead of shutdown, type in this (t instead of r):
shutdown /s /r 0
5. Name your new shortcut, choose an icon for it, then pin it to the Task bar screen.