user does not exist?

I looked into inactive users and seen a user have registered..went to my email and even got new user registration email notice...clicked on it and it says no user exists? whats happened

A glitch.

Hi Skorpy, if you have your members account activation set to "User activation", then it may well be that the member hasn't seen or clicked on the activitation link in their account activation email.
I often get it on my forum, and members have been known to end up creating 2 accounts, because they don't think their registration worked. I think they simply forget to check their email to be honest.