Maybe I missed something, but it doesn't look like the original question was answered.
I, too, have a Win2003 server as a domain controller and cannot get the php pages to pull up, regardless of the browser I use (the one on the server itself, from another PC on the LAN, or from the internet). I get error 403, forbidden access. No matter what I do to the NTFS permissions or the IIS permissions, I still get error 403.
Any suggestions? I just had this working on 2000 Server as a domain controller. PHP is functioning properly (php -i returns page after page of html).