Private login or account authentication, is there a module?

[maniac180]

Is there a way to have a private login or private account authentication?  I want my site to be available to my existing customers for ordering.  I don't want anyone who comes across my site to be able to create an account.  I'd like to create accounts for my existing customers and then give them the login credentials so they can access my site for their use and ordering.  Ideally, I'd like to have a static login page like the attached but without the "Create an Account" and have the "Already Registered" say "Login"

 

Using 1.6.1.15 and basic bootstrap theme.

Edited August 10, 2017 by maniac180 (see edit history)