Do you still have your old computer? Copy your old version of LW onto a disc and load it onto your new computer or you should be able to connect the two and transfer the program over..........
If you can't remember the email address you used to purchase Pro with than your sol. You can either d/load the Basic version or repurchase Pro. If you happen to remember it, click on this link and enter it in and it'll take you to your Pro d/load page:
Lime Wire » LimeWire PRO Lookup
How long since you purchased it. If your free updates has expired, you'll have to repurchase or d/load the Basic(free) version.
Lime Wire » Download LimeWire