Just type in your old email address (the one that you used to buy Pro)

Providing that you bought Pro less than 6 months ago, that should do the trick! If you bought Pro more than 6 months ago, you won't be entitled to updates or email support anyway

If you still have no joy, post back & let us know when you bought Pro & whether or not you paid Limewire LLC for your Pro version (it'll be on your CC statement).