Signup php gone?

Hi…I had modified my signup.php file and the restricted mail notification…but now I notice those files no longer exist though they still function. Where did they go in the upgrade and how can I still change them? I had added a notification to the Restricted Email that a specific account was not allowed…..and made other changes on the signup.php.
When I look at the wp-registration.php file…I dont see anything of what I did…so can someone tell me what happened and where I go to make changes?
thanks…site is healthcrunchies.com