go to
www.grc.com, and download a program called wizmo
go to the wizmo page to see how it works, and you will notice that it has a command to reboot, and a command to FORCE a reboot (in case your computer is crying about it).
Note that it is a command line program, and I have no idea if it'll work on your system or not. I assume it will.
Actually, here's the link right to the page:
http://grc.com/wizmo/wizmo.htm