In php.ini you have to enable extension=php_gd2.dll, or where ever gd is installed too, it will typically be in c:\php\extensions
or in linux #extension=php_gd2.dll
extension=php_gd2.dll
To:
extension=php_gd2.dll
You may also have to correct the extension directory setting from:
extension_dir = "./"
Or:
extension_dir = "./extensions"
I hope that helps