From the admin menu... .you can delete inactive users for x amount of days. Not sure how to delete existing users who have never logged in.
If you turn on email verification in your config file.... new users who register have to follow a link to validate their email address. If they don't validate their email address.... the system deletes the user after like 3 days.... thus removing users that have never logged in.
I already used that option to delete inactive users for x amount of days, but it wont work with user who never login.
Before I had 6.1.1, whitout the option to check e-mail, this is why I have a bunch of users who just create username but never login. I could not find a way to remove them.
If you have access to your database via phpMyAdmin or something similar, you can run the following query:
DELETE FROM w3t_Users WHERE U_Laston = U_Registered
This will delete all the users that never logged in but if you want the query to start from a particular date backwards (cause you don't want to delete users that just registered) you can put an additional WHERE clause like:
DELETE FROM w3t_Users WHERE U_Laston = U_Registered AND U_Registered < UNIX_TIMESTAMP('2002-10-01 00:00:00')
which will remove all the ones that registered and never logged in before the 1st of October 2002.
It occurred to me that although that query gets rid of the users, it won't remove the "Welcome" private messages from the database.
In adduser.php (// Get rid of any unverified email accounts that are over 24 hours old), both get removed, but it requires a loop, and can't be done with a simple query.