Nope, besides uncommenting that line, you need to download the ZIP installation of PHP, not to install it but to get the extentions. Then copy the extentions directory (probably named "extentions") into your php directory. You'd have a "C:\PHP\extentions" directory with files like "php_gd2.dll", etc. Then go to the php.ini and find the line:
extension_dir = /
and change it to :
extension_dir = "c:/php/extensions"
Restart IIS and it should work.
Don't forget to uncomment the extension that you want.