I admit it's a new one to me but a bit of googling suggests that Windows somehow thinks that your desktop is bigger than it is (so that it stretches beyond the edges of what you see actually see on your screen) and the program Window is actually sitting in the 'off screen' area somewhere.
The following solution (which is a direct cut-&-paste from a Microsoft forum, where others thanked the contributor for the answer) might work for you:
- Press SHIFT+CTRL
- Right Click on the Program showing up in the taskbar.
- Select the "Move" Window option
- Use the keyboard (Left Arrow/Right Arrow) keys to move the window to the center of the screen.
- Try holding down the left arrow key for a while to see the Window outline. Try moving right/up/down if the window outline is still not visible.
- Hit enter when you can see the Window outline move to the center of the screen.
[If that doesn't work it might be worth forcing Windows to re-assess the size of your desktop by altering the screen resolution to something other than its current value and then putting it back again. Right-click on the desktop to find the relevant option].