If you ever find the need to reboot a remote computer (when you can’t RDP in) and you need to supply credentials, e.g. for a machine on a different domain, you can’t use the normal:
shutdown /r /m \\COMPUTER
shutdown /r /m \\COMPUTER
To get around this, download the psshutdown tool from Sysinternals and run:
psshutdown -r -u DOMAIN\USER \\COMPUTER
You’ll then be prompted for the password for the specified user (that obviously should have the correct permissions to shut down the remote system!).