You cannot get Pro now. A court injunction is preventing LW distribute their software. If you are a previous LW 5.5 Pro user, then your LW 5.5 will run in pro mode, otherwise it will run as LW basic. LW stopped selling Pro a couple months before the court injunction end last month.
http://www.gnutellaforums.com/instal...r-version.html
The Pirate version of LW will run as Pro anyways.
If you are a windows user & do not like the pirate interface, use File_Girl's adaption of it.