Yes because you don't know how adapted that program might have been. It may even include spyware, etc. Be safer to use the official version from LW.org here http://www.limewire.com/english/content/download.shtml

To uninstall the previous version, go to Start menu >Programs > Limewire > Uninstaller

If you can't find it there then find the program folder & you should be able to find an uninstaller inside it.