This link with the Windows Installer Cleanup Utility works wonders. Thanks.
This was exactly my problem: I keep getting these 2 error messages when I try to install either the limewire update or an all new limewire -
error 1714 (The older version cannot be removed. Consult your technical support group.)
error-1603 fatal error during installation. Consult windows installer help (Msi.chm) or MSDN for more info.
http://support.microsoft.com/default.aspx?kbid=290301