Following on from my Windows XP & 7 guide, Enable RDP using the registry editor, I have created this PowerShell script to automate the task. This script will check if the "Remote Registry" service is started. If it isn't, it'll start it. It will then dig through the registry to find the DWORD we need to change and it'll switch it on/off depending on your parameters.
The registry keys are in the same location, so this PS1 should work for Windows XP & 7 target machines. I assume this means it will work for Windows Vista as well, and probably 8, 8.1 and 10 as well, but these are all untested.
Usage: .\SetRDP.ps1 -PC computername [ -enable | -disable ]