auto_prepend differences W2K pro vs W2K server

Configuration

php 4.3.10

1) Windows 2000 Pro with IIS installed and all recent patches
2) Windows 2000 Advanced Server and all recent patches

Using the following code c:/document_root.php
<?
$_SERVER['DOCUMENT_ROOT'] = "c:/myfile.php";
?>

Within php.ini, specified auto_prepend = "c:/document_root.php"

Well, here's what I found:

- With configuration #1, using phpinfo(), DOCUMENT_ROOT is not specified and is not set.
- With configuration #2, it was?

To solve the problem of DOCUMENT_ROOT with W2K and IIS, I utilized an enviromnent variable setting and then all is fine.

Question - Has any one else encountered this problem with W2K / IIS and DOCUMENT_ROOT? and if so, did you ever solve it other than using an environment variable setting?

Thanx
WP