FastCGI is a language independent, scalable, open extension to CGI that provides high performance without the limitations of server specific APIs. I'm very big fan of FastCGI. Almost all my Apache / Lighttpd servers are powered by php FastCGI.
Today Microsoft announced the official release of their FastCGI extension for IIS server version 5.1 and 6.0. New FastCGI module should improves the performance and reliability of PHP on Windows operating system.
Since early 2006, Microsoft and Zend have been working together on a technical collaboration with the PHP community to significantly enhance the reliability and performance of PHP on Windows Server 2003 and Windows Server 2008. As part of this collaboration, the IIS product group has been working on a new component for IIS6 and IIS7 called FastCGI Extension which will enable IIS to much more effectively host PHP applications.
=> Using FastCGI to Host PHP Applications on IIS 6.0 and IIS 5.1