Depends on when you bought Pro. If you bought Pro less than 6 months ago, go here & enter the email address that you used to buy Pro.
http://sales.limewire.com/support/pro_lookup.php

If you bought Pro more than 6 months ago, you'll have to pay again (your Pro payment entitles you to free updates & email suuport for up to 6 months).

Remember to bookmark your personal download page & save & backup your Pro installers