HTTP Error 404 - File or directory not found.

Hi, I'm relativ new in this mailing-list and also on IIS with PHP. I tried to install PHP 4.3.4 on a Windows Server 2003 with IIS 6. It isn't my first installation of PHP on Windows and IIS, but the first installation on a Windows Server 2003 with the IIS 6. While others installations works fine, with the configuration Windows Server 2003, IIS 6 and PHP 4.3.4 the error "HTTP Error 404 - File or directory not found" occurs. I tried several things to eliminate the error or isolate the problem. - First .html in the same directory are found and displayed. - Second, I looked after the permissions of the needed files. - Third I assured that the mapping from .php-Files to php.exe exists. Now, I don't know where I can or should search for the problem. What's the next thing to find the fault in the configuration? Where should I search for a solution or have had someone the same problems with this configuration? Thanks a lot for your help. Best regards Manfred