Generation of Authentication key

I want to deploy my product to users on a CD. I want to create a CD key or registration key for the same. Do you know any of the technique ?
Thanks in advance
Sachin

http://www.freevbcode.com/ShowCode.Asp?ID=1639

http://www.freevbcode.com/ShowCode.Asp?ID=2232

http://www.freevbcode.com/ShowCode.Asp?ID=662