- Use ALTTAB to switch to the off-screen application.
 - Press ALTSPACE to bring up the system menu (you won't see it because it is off screen)
 - Press R to select the "Restore" menu choice to ensure the windows isn't is maximized (you can not move it if it is maximized)
 - Press ALTSPACE again, then M to select the "Move" menu choice.
 - Press one of the arrow keys to initiate the movement.
 - Now just use the mouse to place the window where you want.
 
If you are using a non-english version of Windows, the "R" and "M" menu choices probably wil be different.
