I have seen that a lot of people visit this site when searching for:
Handler "PHP_via_FastCGI1" has a bad module "FastCgiModule" in its module list.
So, here's how to fix it.
1. Go to Control Panel -> Programs and Features -> Turn Windows features on or off
2. Scroll to Internet Information Services -> World Wide Web Services -> Application Development Features
3. Turn on CGI
4. Wait a bit
For more information how to configure PHP on IIS visit Installation on Windows systems on php.net.