Advanced Registration is a registration overhaul to vBulletin which aims to improve the registration process by adding essential features, such as guest redirects, and improving on the original system.
It supports an invite system, verify email before registration, all of which are compatible with open or closed registration, a registration page overhaul - allowing you to completely change the order and display of all fields.
Advanced Registration allows for heavily tracking all registration related data - from errors to successful registrations.