First of all, did you buy Pro for $18.88 from www.limewire.com?
If you bought Pro from the official site, you should've recieved an email with a link to your personal download page... did you ever enter any email address at any stage of the purchase?
Are you sure that you saved the installer?

If you did buy from the official site, check through the thread below... there are a few links to help. You might have to send a PM to RSterne & ask her to help you sort things out!
http://www.gnutellaforums.com/showth...threadid=54008

If you bought from another site, read through the thread below about membership scams
http://www.gnutellaforums.com/showth...threadid=28751