Regedit
Connect to remote registry
Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server] "fDenyTSConnections"=dword:00000000
Then reboot the machine remotely, e.g.
shutdown -m \\yourserver -r -t 0
Thnx to my mate at http://www.tech-notes.nl