I have successfully installed PHP5.3 but cannot seem to get it to work on IIS7. I have followed the tutorial on iis.net (http://learn.iis.net/page.aspx/246/using-fastcgi-to-host-php-applications-on-iis-70/) and can clearly see in the IIS Console that the mapping for *.php files should execute php-cgi.exe as a Fast CGI module. However, when I try to load a php page in my browser, I see no output. Any suggestions on how to debug this?
There is a forum post over at iis.net where wendac give instructions on how he got your same situation to work: Vista x64, IIS 7 and PHP 5.
I would think that the most important step that you might be missing is step 6: