user registration form

use these tutorial
http://drupal.org/node/335020
or try this module
http://drupal.org/project/contact_form_on_node

I think what you mean is that you want to set it so that when non-logged in users visit your site, you want them to see just a login/registration form. If this is the case, then try this:

1. Log into the admin account
2. Click "Configuration"
3. Click "Site Administration"
4. Set the default 403 error page to "user/login" or "user/register" (whichever screen you want to popup first

Also you need to make sure that your homepage restricts access from anonymous users. I did this by installing the Views module to emulate the homepage and then restricted access to my new emulated homepage.

Hope this helps.

-- Chris