<?$APPLICATION->IncludeComponent(
                        "bitrix:system.auth.form",
                        "demo",
                        Array(
                          "FORGOT_PASSWORD_URL" => "/login/?forgot_password=yes",
                          "PROFILE_URL" => "/login/user.php",
                          "REGISTER_URL" =>"/login/?register=yes",
                          "SHOW_ERRORS" => "N"
                        )
                      );?>"REGISTER_URL" =>"/login/?register=yes",?register=yes подключит system.auth.registration (регистрация),.