Did you buy your original Pro from www.limewire.com? It sounds like you might've been scammed...there's no registration code for the official Pro & your payment of $18.88 USD covers you for 6 months of updates & email support only.
If you bought from a scam site, your email address would never have been in the LW database & after 2 years it would definitely be gone (even if you did buy an official version).

You can download the latest LW basic (free) version from the link above. If your old version was from 2 years ago, you should try the free version before thinking about buying Pro...a lot has changed since then!!