If you bought Pro from www.limewire.com (the official site) less than 6 months ago, you can use your personal download link to download the Pro installer. If you haven't bookmarked your personal download link, go here & enter the email address that you used when buying Pro.
http://sales.limewire.com/support/pro_lookup.php

If you bought Pro more than 6 months ago & don't have a Pro installer saved, you'll have to pay again to get Pro. Your LW Pro payment of $18.88 entitles you to free updates & email support for 6 months