[FX.php List] why MICROSOFT IIS TWEAKS

[Someone]

Hi
Can anyone explain why MICROSOFT IIS TWEAKS is needed.
Why not just have -> include_once("FX.php");

I'm getting an error with the below method
Notice: Undefined index: PATH_TRANSLATED in c:\Inetpub\wwwroot 
\ztest.php on line 19

// MICROSOFT IIS TWEAKS

if (! isset($_SERVER['DOCUMENT_ROOT'])) {
     global $DOCUMENT_ROOT;
     global $HTTP_SERVER_VARS;

     $_SERVER['DOCUMENT_ROOT'] = str_replace(str_replace('\\\\', '/',  
$_SERVER['PHP_SELF']), '', str_replace('\\\\', '/', $_SERVER 
['PATH_TRANSLATED'])) . '/';
     $DOCUMENT_ROOT = $_SERVER['DOCUMENT_ROOT'];
     $HTTP_SERVER_VARS['DOCUMENT_ROOT'] = $_SERVER['DOCUMENT_ROOT'];
}

// END MICROSOFT IIS TWEAKS
include_once($_SERVER['DOCUMENT_ROOT'] ."FX.php");

Thanks
Frank