PHP Windows install keep getting error 404 file not found

I have a Windows 2003 with IIS 6 working (other non-php web sites are being served properly by this server). Followed the PHP install procedure described at www.peterguy.com web site to the letter. If I try PHP active script, PHP active script works. If I try to open a php web page I get error 404 file not found. The php web page does exist and if I change the extension to html I can view the web page as text. The problem seems to be that IIS does not know what to do with a PHP document. I have added the extension and installed it for the web site.as described in the install procedure. I am using the isapi dll. Is there a way to test the isapi dll? I have installed a test.php page which is supposed to show the php configuration. However every time I try to access this web page I get error 404. I tried several other test php and info-php files with the same error happening. What else can I do to get IIS to run the php script? Any help would be appreciated. Charles Bujold