You will need to setup one or two servers with Windows 2003 Server or Windows 2003 Small Business Server.
You will need to make the server a DNS server, and DHCP server.
After you have the Server software installed you need to need to run dcpromo to make the server a domain controller.
Then setup each workstation with the server as the primary DNS server. Then add each workstation to the domain.
if you are using DHCP on the domain controller just make sure that each pc is using DHCP to get their IP address and that you set the SERVER OPTIONS in DHCP to give each computer the address of the DNS server. then they will receive it automatically.