I'm running Windows 7 and every now and then I end up with an item from a menu or combo box floating on my screen. It's like a little lost puppy that can't find its way home, only way more annoying. The left over drek typically clutters my screen until I restart. I found an easier way for the widget to find its way back home:
Under Control->Panels –>Performance Information and Tools->Adjust Visual Effects
Turn off the checkbox for Use Visual Styles on Windows and Buttons. It takes a minute or more to reconfigure your display, be patient. I then turn it back on. In the meantime the floating widget found its rightful place and is no longer hanging around on my screen.