Hello myibay, I have bought a key a few years ago. But now I don't remember it. Please send it to me again. I used paypal for making payment, email is Thank you so much.

You can always download the software using the following link:
http://www.myibidder.com/download/

Once installed, login using the same eBay user id you specified when made the purchase so the software will recognize you automatically and register itself.
You can check if registration was successful by clicking Help - About menu. You should see "Registered <your eBay user id>".