Bring Misplaced Off-Screen Windows Back to Your Desktop (Keyboard Trick)

Set your "hidden" window to focus (using alt-tab for example), then press Alt+Space, then M, and then hit any of the arrow keys (Left, Right, Up or Down), move your mouse and the window should magically "pop" back onto the screen. This should work on any version of Windows.

Update: You can also right-click on the taskbar and choose to "Cascade" your open windows, which will often help bring the windows back onto the screen.

Taken from HowToGeek.
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