DNS resolution

Hi guy’s. I setup a NT4 server with DHCP, WINS and DNS. I can ping and resolve any local host fine therefore I added a fowarder in my DNS configuration pointing to my ISP’s DNS server. However local workstation still cannot resolve ‘yahoo.com’ for example. I have tcpip ip fowarding turned on. Do I need a proxy server in order to ping out to the internet via my NT server ?