Enabling PHP on IIS 5.1 or higher

Install PHP from www.php.iis.net
In IIS
Open properties of default website

1. Select the HOME directory and click configuration button
2. Click Add on mapping tab (browse to C:\Windows32\inetserv\fcgiext.dll. Enter .php in Extension input box. Set limits to "GET, HEAD, POST".  
3. Restart IIS.