In the Windows Start Menu choose "Run:", type "inetmgr" and click "Ok";

In the IIS Manager user interface select the server node in the "Connections" tree view;

In the "Features View" page open the "Handler Mappings" feature;       

In the "Actions" pane click "Add Module Mapping...";

In the "Add Module Mapping" dialog enter the following:

• Request path: *.php
• Module: FastCgiModule
• Executable: C:\[Path to PHP installation]\php-cgi.exe
• Name: PHP_via_FastCGI

Click "Request Restrictions" button and then configure the mapping to invoke handler only if request is mapped to a file or a folder;       

Click OK on all the dialogs to save the configuration.