Recently I found myself stuck trying to remotely control a Server 2012 R2 Hyper-V server using RDP. Somehow, I managed to reconnect to an RDP session in which I had left one of the Hyper-V connection windows maximized. When I subsequently reconnected, all I could see was that single Hyper-V connection session and nothing else. To make matters worse, I couldn’t see the taskbar for the Hyper-V connect session as I only could see the task bar for my RDP session. Luckily, I happened upon the following fix posted by Nick Aquino on a Technet blog:
I found a workaround: When I RDP to my host and one of my HyperV VM sessions was sitting on the host in Full-Screen mode, I had a problem exiting the VM session so I could access my host. My workaround was to Press CTRL+ALT+END (to simulate a CTRL+ALT+DELETE) on the host and launch Task Manager. This shows the task-bar at the bottom, where I can mouse over and close. When I open the VM session, it will not be in FULL screen mode.
Thank you Nick!