Getting registration form add on to replace wp/buddy press registration

I am a little confused. My site is currently requiring a registration for all users. I am not sure if that is a standard feature, or if that has been triggered by the Members plugin. In any event I am also trying to get the login screen registration link to redirect to my Gravity registration form. Could you provide a step by step explanation as to how to get wordpress/buddypress to use my form from the registration link on the login page? I am currently using wp 3.1 and I already have the form all setup...

Thanks,

I figured out why it was requiring registration (it was an option that was enabled with the Members plugin). I have turned that off, and now users can view pages without having to first register.

As far as implementing the add in, there is no register.php file in the theme folder. I am seeing a form in the wp-login.php, but it is not clear how to switch it to the gravity form. It is the original registration form. Any idea how I would swap it out for the Gravity form?