If you can't find it in htdocs/config.php then you have the wrong config.
Then download the new config or add these lines :
PHP:
//ReCapatha http://recaptcha.net/whyrecaptcha.html
$config['site']['publickey'] = "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"; // Public Key
$config['site']['privkey'] = "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";; // Private Key