The php_pdo_mysql.dll can\'t be enabled in machine. I have set extension=php_pdo.dll and extension=php_pdo_mysql.dll enabled in php.in
If you're using PHP Manager with IIS, do the following:
Open IIS (I usually open it by typing IIS in start);

Double-click "PHP Manager";

Click "Enable or disable an extension";

Scroll down to find your driver of choice (in my case php_pdo_mysqll.dll), and click "enable";

After that the driver should show up, and work.

Done! Hopefully this helped someone, because the other answers did not work for me.