If I understand correctly, your window is off of your screen so that you can no longer see the maximize button. If this is the case, press Alt + spacebar then M and use the arrow keys to move your window down.
If you mean the UG graphics window, try Preferences-User Interface and press the Reset Windows button.
"Wildfires are dangerous, hard to control, and economically catastrophic."
"Fixed in the next release" should replace "Product First" as the PTC slogan.