If you reinstall, the installer will remove the previous version at the beginning of the installation process. Otherwise, go to Start menu, Programs>Limewire>Uninstall. You cannot uninstall LW using Add/Remove control panel.

You might also want to try deleting your LW Preferences folder whilst LW is closed; instructions here: Point #2 & 3 in Fixes for Limewire (sample image included at bottom of page.) As LW's preferences might be corrupted.