Some time ago, I showed how to get a window back on the screen when it moved far, far away. That technique still works in Windows 7 and 8, but there's an easier shortcut that takes advantage of window arrangement features added in Windows 7.
First, you switch to the application by whatever means. Then hit Win+UpArrow to maximize the window. That should put the window on-screen, albeit at the wrong size. Now you just grab the title bar of the window with the mouse and drag it off the top edge of the screen. Bingo, the window returns to its original position, and you can use the mouse to put it wherever you like.
This trick doesn't work for windows that cannot be resized (such as Calculator), but for those windows, you can use the old version of the trick.