If you allow telnet access and your RDP sessions are all locked up (from pesky admins disconnecting and not logging out), there are a few tools that you can use from the CLI. One tool is called query, this tool allows you to see who is all logged in. The usage is 'query session' and you will get the output of who is logged in and what ID's they are using.

Another command is tsdiscon and you pass it in the session_id of the person you want to disconnect. Mind you though using this command sometimes doesn't disconnect the user because the connection could be hung up.

If that is the case then there is the ever so wonderful 'tsshutdn /reboot', which (provided you give it a few minutes) will restart the terminal services client.

All of these work really well over a connection that uses SSH (such as FreeSSHd or Cygwin).

More information can be found at http://technet2.microsoft.com/windowsserver/en/library/2b82a2b9-e226-40e0-bacc-cb564bd4c1c11033.mspx?mfr=true and http://support.microsoft.com/kb/320188