I guess it depends upon how old your previous version of LW was. If it was older than version 4.4 then go to your Add/Remove control panel & remove the older version of LW. Make sure you don't have any other versions of LW on your computer. Go to Start menu>Programs>LW>Uninstall. Then search your computer for the word limewire. Make sure there's no LW programs still there. Then reinstall LW.

Also delete your LW Preferences folder whilst LW is closed before reinstalling; instructions here: Fixes for Limewire