Joe,
It sounds like there might be some error window or dialog window that's popped up on the area of the window that's off screen and out of view. If that's the case, usually that window has to be dismissed before you can do anything with the main window. What might work is to use one of the stupid Windows tricks (apologies to David Letterman's Stupid Pet Tricks and Stupid Human Tricks).
Make sure the main window has focus. You can do this by clicking in the window since at least some of it is visible. Then hold the window key and press the up-arrow key. This should maximize the main window. If so, you should be able to deal with whatever window that popped up demanding your attention.
This often, but not only works when you've had two monitors connected and closed a program while it's on the second monitor. Many programs will start up wanting to run where they were shut down and if you start it again without the second monitor attached, you can't drag it to the monitor that is attached. In this case, make sure you have focus by clicking on it in the task bar. Then use Windows key + right or left arrow to move it horizontally. You may have to hit it several times because it will first move the window to the edge of its current monitor before moving it to the other monitor.
I've found that it doesn't work for some programs, but it works for more of them than not.
73,
Larry K8MU