Here is how to mess with your computer and I do not take any responsibility for any damage you might do.
Open an Admin Command Prompt. A regular prompt for an Admin User should work as well.
Type the following command then press enter: shutdown /p and then press Enter.
Your computer should now shut down immediately without installing or processing any updates.
Type Shutdown /? for all the parameters that the Shutdown command can process.
Good luck and remember that if you are successful in not doing updates on shutdown, they will happen on startup (probably 2 cycles with attendant restarts along the way).