If you still have your LW installer .exe, then you might burn it on CD. You could also use your old HDD as a slave and after installing your OS on your new one you could copy the installer .exe from the slave drive.
To purchase a new Pro with full 6 months updates and tech. support, go to the official LW site (of course after having your new HDD ready), and go to the purchase process which will (after completing) provide you with your personal download mirror for the new installer .exe.
http://www.limewire.com/ 