I wanted to be able to have customer register on my site, but I didn't want the "create a new acount" visible. So I went to settings, and created a new template for the login page.

1. go to settings
2. go to the 'user' tab
3. enable "Anonymous Registration"
4. Save
   
5. go to "authentication" tab
6. click on the "manage" button for the "login template" drop list
   
7. duplicate the default template
8. edit the new template by removing the anonymousRegistration link code:
   <tmpl_if anonymousRegistration.isAllowed>
            <li><a href="<tmpl_var createAccount.url>"><tmpl_var createAccount.label></a></li>
   </tmpl_if>
9. save.
10. commit your changes
    
11. Go back to settings and use the new login page template you just created.
    

 (written using 7.5)