Изменить путь к регистрации

            $row['template'] = str_replace( "{%validationlink%}", $config['http_home_url'] . "index.php?do=register&doaction=validating&id=" . $idlink, $row['template'] );

            msgbox( $lang['all_info'], $lang['confirm_ok'] . "<br /><br /><a href=\"" . $config['http_home_url'] . "index.php?do=register&doaction=validating&step=2&id=" . rawurlencode( $_REQUEST['id'] ) . "\">" . $lang['reg_next'] . "</a>" );

$tpl->set( '{registration-link}', $PHP_SELF . "?do=register" );

            if( $_GET['page'] == "dle-rules-page" ) if( $do != "register" ) {

/engine/engine.php

case "register" :
include ENGINE_DIR . '/modules/register.php';
break;

или же через чпу
в корне сайта .htaccess

после
RewriteRule ^rules.html$ index.php?do=rules [L]
добавить 
RewriteRule ^register.html$ index.php??do=register [L]