windows does a horrible job of recognizing that a monitor is gone but sending your program’s window to it. (Example would be if you have a laptop in a dock with 2 monitors at work, but at home you just use the laptop display – not an unheard of pattern of use.) In the pre W7 days, you could right click on it in the taskbar, choose “move” and then arrow key the thing around, unfortunately in W7 they took that away. It took me a whole lot of searching to find a solution, and it was in the comments of a post about the old trick in Vista. So, the trick is:
If you hit the Windows Logo Key plus the left or right arrow keys it snaps the off-screen window to the left or right side of the desktop (of the “active” display).