Port 80 Blocked, Windows XP

Hello, I really love the site and I reference it frequently when I am working on machines for different clients. However, I've got a machine that can't get to any http sites. I read your article on the subject of unblocking port 80 and it seems textbook--he once had the Cisco VPN client installed, he can access https but not http... However, when I enter the registry, there is no entry called vsdatant in the path you specified. This is XP Home, if that makes a difference for this. Any advice on getting this port opened?