From: http://mediarealm.com.au/articles/2013/03/remotely-enable-remote-desktop-in-windows-7/
Step 3: Change a registry setting to enable Remote Desktop It’s time to make use of the Remote Registry and actually enable RDP. Load up regedit and go to File > Connect Network Registry. Enter the name of your remote computer and connect to it. Navigate to HKEY_LOCAL_MACHINE > System > CurrentControlSet > Control > Terminal Server. Change the value of “fDenyTSConnections” to “0”.