You’ve closed the Hyper-V Server 2008 R2 Server Configuration menu and need to re-open it:
The command to re-open this window has changed with the R2 release. The new command is sconfig.cmd, with the non-R2 version, the command was hvconfig.cmd. Start Windows Task Manager by pressing Ctrl & Shift & Esc. Click File>New Task:
Type cmd.exe /k C:\Windows\system32\sconfig.cmd and click ok:
You now have a new Server Configuration window:
Simply entering sconfig.cmd in the command prompt window will work, but you’ll lose your command prompt window so it is a less than desirable solution.