On the Server
Start button>Administrative Tools>Make sure that DNS is in the menu.
Once you have determined that DNS is in that menu (and therefore installed), open a command prompt, and type the following:
ipconfig /all
Make note of the hostname.
Make note of the IP address
Make sure that the DNS server's IP address listed is the same as its own IP address (The Domain Controllers DNS server is itself).
On WinXP machine
Run...
\\Domain controllers' hostname
if that didnt work, then:
\\Domain controllers' IP address.