2000DNS/ FQDN

Hello,
I have the same domain name for my Windows 2000 Domain Controller ( XYZ ) which is in the Private Network and the same website name which is also (http://www.xyz.com). The problem is when my users ( in Lan) trie sto browse www.xyz.com, it can’t find it, but if they were to use dialup connection, they can browse it. It appears my Windows 2000 DNS and my FQDN is conflicting. How can I fix this issue?

Thank you
SP