You should have received and e-mail with a link to your pro page.
You can re-dowload from that link. The link should be good for six months from when you received it.

If you you don't have the link any more, and your still within your six months, you can look it up here. http://www.limewire.com/english/cont...pro_lookup.jsp

If you are beyond your six months you can still download the basic version for free.