In the future, do this to "recover" lost-off-screen windows. (It happens to me all the time with stoopid Windows Photo Viewer....)
0) Try to assure that the window in question has "focus." I.e. It is selected somehow.
1) Press <ALT>+<SPACEBAR>. This will open the regular Windows menu for moving the window to another place. If, when you press <ALT>+<SPACEBAR>, you cannot see the Window, you only see the popup menu, press <DOWN ARROW> once and then <ENTER>.
2) Now you can use the arrow keys to move the window to a position where you can see it.
You might want to exit the window NOW, and restart the application to assure that it remembers the new ON-SCREEN position tho!
Voila!