How php in ISAPI mode?

Hello, I am trying to install PHP in ISAPI mode and no in CGI mode. Some time ago I intalled PHP 4.4.3 on a W2000 IIS 5.0 in ISAPI mode without any problem but now I wonder if it was only luck :( I followed instructions about cgi.force_redirect=0 in php.ini and using the IIS manager I added php4isapi.dll in filters and for extension .php. I thought these steps allowed PHP to work as ISAPI module. Now I deal with PHP 4.4.7 on a W2003 IIS 6.0. I have checked cgi.force_redirect, filters and extension .php but the browser gives a 404 error for any php request. I have found using phpinfo() that the main diference between this installation and the correct one is that on W2003 PHP is in CGI mode and I guess that if it was in ISAPI mode it wouldn't give the 404 error. ¿What I must check to configure it in ISAPI mode? Thanks.