Windows Server 2012 GUI went missing after removing Active Directory
Solution 1:
Is explorer simply not starting? have you tried typing explorer.exe
in the command prompt window? I guess this isn't the case you wouldn't normally get a command prompt when logging in. It sounds like somehow the shell has been removed, effectively giving you a server core install, in which case try issuing the following from the command prompt. This should re-enable the shell if it has been somehow disabled.
Dism /online /enable-feature /featurename:Server-Gui-Mgmt /featurename:Server-Gui-Shell /featurename:ServerCore-FullServer
Solution 2:
FYI, when this happened to me, I kept getting an Error 50 when using the command above. I had to add an /all to make it work. Once I did that, it worked just fine.
Dism /online /enable-feature /all /featurename:Server-Gui-Mgmt /featurename:Server-Gui-Shell /featurename:ServerCore-FullServer