Need some Visual Basic help

[21C]

VB 6 to be exact.

I've made a few programs for myself over the years and even made a couple that I've shared as freeware. But I've just made a program for my school that they have found useful and are prepared to pay me for.

And that is what I need help with. I need to somehow protect the program with some sort of registration/serial number but I've never had to do this before. I know I need to get some sort of unique registration code that generates a matching code and then possibly store this all in the registry but I haven't been able to track down any code.

Has anyone had any experience with this and is able to share some ideas or code to accomplish this?