See: http://i.imgur.com/pQNQh.png
Somehow I made this happen and I don't know how to undo it. The image linked above shows my Flex Builder session. The largest section of the window is the editor. Initially, there was a blank window on the screen so I tried closing it, but I couldn't. Then I tried dragging it and realized I could drag it into a corner of itself, hence all the nested windows.
I have no idea how to close these windows or simply reset the view. I went to the preferences under General > Perspectives, but the "reset" button was disabled for every available perspective.
Help?