Change Windows Server 2012 Product Key

 Windows did not allow me to change the key from any of the GUI's

Use the PowerShell....

1.	Clear The Current Key Open Powershell with admin rights then enter: slmgr -upk (this removes the current Product Key)
2.	Add The New (or Correct Key) Now that the key is cleared you can either stay in Powershell and enter the new key with the following: slmgr -ipk XXXX-XXXX-XXXX-XXXX (with the X's of course being the Key ) or Go the the activation GUI and you will now be able to enter a Key