Open Internet Explorer, go to Tools/Internet Options, then the Connections tab and finally to LAN Settings button. The check box for use a proxy sever ... should not be checked.
You can also do a nslookup from a command prompt to find the IP address of the site your are trying to reach. Armed with the IP address type or paste it into IE address bar. That will verfiy DNS is working.
Edited by ratchet48, 20 December 2009 - 01:14 PM.