Need code/advice on password protecting VB6 program

Hi there,

I am selling my program online (advertised online, I post VB6 CD to user, not online sales) and I want my VB6 program to retrieve the customer's hardware ID number, then they email me there hardware ID number, then I enter there hardware ID number into an algorithm program at my end and I email them back a password (based on their algorithm). The password I email them allows them access to my program and prevent users from making pirate copies for other users because it only works on one computer per hardware ID number.

Any advice, links, ideas etc is appreciated...

Simon