Can someone please tell me any good script for incorporating a user registration system on a site
It should have facility to let the user register Check for duplicate reistration & other simple essential features
This is not for passowrd protection
That would be more than enough. Just create a page with the join/login form on it and send the info to a php script. If they are joining, check to make sure that no other member has that email address (or whatever you use as a username). If the email address is not in you database then add them, create a session id/cookie and redirect to the member section. If the email address is already there, let them know and offer to log them in. The login version is the same in reverse.
Let me know if you need any specifics and I will send you some code.