Just temporarily change your monitor setting to a larger size. This will make everything on the screen smaller & fit onto screen. Then you can drag it across to the middle of screen. Then change the monitor size back. Actually OSX gives you 15 secs to make your decision of monitor size & if you don't press ok then it will revert back to the previous setting.

Other option is to delete the LW preferences whilst LW is closed & found here: /Users/your_username/Library/Preferences/LimeWire
But if you choose this option then you should make a note of all your LW settings 1st b/c after deletion you'll need to reset the options.