I want to offer a free product on my site for everyone that refers new people.

I have heard of the refer a friend script but what about one that also registers them to win a prize?

Does the script actually choose the winner or not? If not, how to I choose a winner fairly.

Thanks for any help

That should have said "I want to offer a chance to win a free product for anyone that refers new people to my site"

Thanks for any advice