Run a PHP script that contains phpinfo() and look for a section named curl. If it exists then the cURL extension exists, and the section will give you information about the specific version of cURL it has been built against.
I fixed it... I was editing the php.ini file located in c:\program files\php. And it was actually using a different php.ini file located in the Windows folder. Not sure why there would be two of them, but it's all sorted now!