Create Account Page Modifications
When a store has enabled the OPC's registered-account handling (setting Configuration :: One-Page Checkout Settings :: Enable Account Registration? to true), the formatting of the store's create_account page is modified to gather minimal customer information with which to create an account. Upon click of the "Register" button (and validation of the entries), the customer's account is created — with a place-holder address-book record — and the OPC's modified version of the create_account_success page is displayed.
The customer can optionally add an address to their account by navigating to their "Address Book". Upon entry to the checkout-process, the customer is required to supply the address(es) to be used for their order.
The language-text associated with the changes is found in includes/languages/english/lang.create_account_register.php and the page-template is found in includes/templates/template_default/templates/tpl_create_account_register.php.