Windows – How to open the Windows Task Manager during a Remote Desktop session

Do you have the option of running AutoHotkey on the remote PC? You could run a script there which would trap an alternate hotkey of your choosing, and render it (there) as Ctrl+Alt+End.

Ctrl+Alt+Pause will take the RDP client out of full-screen mode, it should only work on the current one. Once you minimize the inner RDP, you can Alt+Tab to other windows in the external RDP. Switching back to the inner RDP and clicking Ctrl+Alt+Pause will maximize it again.

Also, if you are using Windows 7 or have Remote Desktop Connection 7 installed, you can move the "pop down thing" before you open the second RDP client. That way you have them side-by-side and not one on top of the other.