http://oreilly.com/windows/archive/server-hacks-remote-desktop.html
HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server
Under the Terminal Server key, you’ll find a REG_DWORD value named fDenyTSConnection. Double-click on that value to open the Edit DWORD Value box and change the value data from 1 (Remote Desktop disabled) to 0 (Remote Desktop enabled)