Well this can and has happened to the best of us. We had a new tech working on a server, and he just disconnected instead of logging off. I knew there was a work-around to get in, and it took me longer than I felt it should to figure out. Most of the immediate stuff coming up in Google is all about Windows home server. In order to get in, you simply need to go to Command prompt, and run:
mstsc /v:xxx.xxx.xxx.xxx /f -admin
Be sure to replace the xxx.xxx.xxx.xxx with your server’s IP Address.
Once in, it is important you go straight to Task Manager and log off the other users. If you disconnect while logged in this way, you will be forced to hook up a keyboard, mouse, and monitor to the physical machine.
(Source: Skynet Solutions)
By Jed Parmenter