wordpress plugin for user registration with referral id

Question

I need any idea or wordpress plugin suggestion for user registration.

Users will sign up and site will generate a username and password which will be emailed to user. New users must submit the customer number of who referred them in order to complete the sign up process without any commission process.

ie., user must enter email address and referral id to signup and should get email of auto generated username and password.

Is there any idea for user registration with these process?

Answer 1

S2member plugin may fulfil your needs I suppose http://wordpress.org/plugins/s2member/.