register filters the HTML link to the Registration or Admin page. Users are sent to the admin page if logged-in, or the registration page if enabled and logged-out. This filter is part of the wp_register() function.
The following changes the register link:
add_filter( 'register', 'my_register_link' );
function my_register_link( $link ) {
return 'http://exampledomain.com/my_register_page/';
}
Since: 1.5
register is located in wp-includes/general-template.php