Need help with index.php

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I've change from default.php to index.php with 3 steps:

Step 1 - Rename catalog/default.php to index.php 
Step 2 - Rename catalog/includes/languages/YOUR LANGUAGE/default.php to index.php 
Step 3 - Open catalog/includes/application_top.php and change define('FILENAME_DEFAULT', 'default.php'); 
to define('FILENAME_DEFAULT', 'index.php');

 But it still no work when I type: http://www.xzzzxsoft.net/catalog/ 
 then I have to type: http://www.xzzzxsoft.net/catalog/index.php it work.

 How can I fix it ???

 Thanks.