Messages

Hi,
I just installed abantecart on win7 under xampp.
everything went fine.
when I try to use the system/data/export functionality I get :
Class 'Atargz' not found in ....abantecart_v1.1.5\public_html\core\lib\data.php on line 253.
I do see the data.php file.
What should i do?
Thanks.