PHP & IIS on XP Question

I installed the latest version of PHP (Windows Installer) on my Windows XP
Pro / IIS development machine. I have a Virtual Directory for my web site -
the directory is configured to use index.php as my home page. I can run PHP
script from this directory or any of its subdirectories AS LONG AS I name
the page index.php AND do not specify the page name in my browser. I can
upload my page to my host ISP - it runs fine there even if I specify the
page name in the URL. What is missing in my configuration to make the page
work properly (if not named index.php and if the page name is specified in
the URL).

Thanks!

Bryan
www.save-u.com