External DNS on a 2003 Server

The users on our network are complaining about slow Internet, takes 40 seconds to fully load CNN.com. We have a 4.5Mb T1 connection. Our DC is the internal DNS server and it’s all behind a SonicWall firewall. There are no forwarders set up and even if I remove the external DNS setting on the firewall, we can still surf the Internet. Where do I find the address of the External DNS server we’re using? There are root hints, but not for all letters.

Thank you for any help!