I cannot remember the name of the .exe that shuts windows down, but using it and a simple batch file along with Task Scheduler, this should be easy.
Edit: What OS are you running?
If XP, open up notepad, and copy one of the two commands here...
For a shortcut to RESTART Windows XP:
SHUTDOWN -r -t 01
For a shortcut to SHUT DOWN Windows XP:
SHUTDOWN -s -t 01
Save the file with a .bat extension rather than a .txt. Then use Scheduled Tasks to run that .bat file when you want it ran.