Download the latest PHP version for Windows from http://www.php.net/downloads.php, right-click on the PHP folder, and select "Extract All..."
Choose C:\Program Files\PHP5 as extract directory and click on "Next"
Uncheck "Show extracted files" and click on "Finish"
Launch the "Internet Information Services (IIS) Manager" from the start menu. You need to install IIS in case this option is not available.
Right-click on "Website" and select "Properties"
Select the "Home Directory" tab and choose "Configuration"
Add "C:\Program Files\PHP5\php5isapi.dll" (including quotes) to "Executable" and add .php as extension. Then limit the verbs to GET,HEAD,POST,TRACE and click on OK
Now choose the "Documents" tab and select "Add"
Enter index.php and click on OK
Now, you can change the priority of your index.php with the "Move Up" button. This is only necessary if you run primary a PHP based website
Finally, select Web Service Extensions on the left side and choose "Add a new Web service extension"
Select "Add" and enter as path C:\Program Files\PHP5\php5isapi.dll and click on OK
Then enter php5 as extension name and check "Set extension status to Allowed". Then click on OK to enable this extension
Copy C:\Program Files\PHP5\php.ini-dist to C:\WINDOWS\php.ini and restart IIS
Then create the following php file with Notepad:
Save this file under C:\Inetpub\wwwroot\test.php
Now launch Internet Explorer and go to http://localhost/test.php . You should see the PHP info page if your PHP5 installation was successfully.