If you are talking about DNS domains, each domain as registered will have an authoritative server registered, and the whois command will show you that. That address is where the DNS system will go for an "authoritave" answer. If that address is not your server (or a DNS server of your ISP, who is maintaining DNS information for you), you need to correct that before anything else.
It is possible (and often done) to have an official "Public" DNS server, but to have a separate DNS server inside your network which knows things that you do not want the world to know. In this case, the boxes on your LAN point to the private DNS server, which is set up to think it is the authoritative primary server. Anyone looking you up by coming down from the root servers will find answers from the "Public" DNS server.
A separate problem is whether or not each machine is looking at ANY server.
In NT, from a command window, type:
ipconfig /all
This will list the DNS servers which your machine is using (where they will go to look up names). Note that this may be different on each machine. (On windows 95/98, use winipcfg.)
If you are running DNS server on your NT, if your DNS server as reported by ipconfig is not your NT box address, you first need to change that (network properties).
Use nslookup to query the DNS. Start nslookup, and type help for a list of commands.
Good luck.