This guide has been updated and rewritten as the easiest way to successfully Configure IIS 7.5 to work with FastCGI and PHP on Windows 7 is to use
Microsoft Web Platform Installer 2.0 from http://www.microsoft.com/web/Downloads/platform.aspx
Why?
The installer does all the hard work
No more downloading PHP then configuring the php.ini file
No more going into your Internet Information Services (IIS) Manager and adding a Handler Mapping FastCGI Module
No more going into your System Properties and setting up your Environmental Variables
No more spending endless hours surfing around looking for solutions that help you get it all working (it rarely happens first time)