If you bought Pro less than 6 months ago, either follow your personal download link, or go here & enter the email address that you used to buy Pro.
http://sales.limewire.com/support/pro_lookup.php

If you bought Pro more than 6 months ago, you'll need to buy again (your Pro payment entitles you to free updates for up to 6 months). The only official site for buying Pro is Lime Wire » Official Website & Free Download «

To protect yourself, always make sure that you're using a good AV program. Keep it updated & scan files that you've downloaded before you open them
WARNING: Viruses on the network you should be aware of