what do you mean "frozen"? Do you mean you are using Deep Freeze?
If you aren't setup for remote administration via gpo or other then a bad choice was made and has to be corrected before you can do as you wish.
Though you should be able to run shutdown.exe without employing a gpo but you do need to input the host name in the command. Not sure if you can use ip address instead of name. The remote host has to be identified or the command assumes the local host.