LoRz

Search for all the PHP ini files in the XAMMP directory including php4.ini/php5.ini

Look for the lines

;extension=php_curl.dll
;extension=php_openssl.dll

Uncomment the lines to enable the extension

extension=php_curl.dll
extension=php_openssl.dll

Restart Apache. To verify, you should see in the PHP info [phpinfo();] that cURL is enabled or you could try testing the following code

<?php

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, "http://www.google.com/");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$output = curl_exec($ch);

curl_close($ch);

$output = str_replace('Google', 'Test', $output);

echo $output;

?>