cannot add my windows 2000pro computer t

Is this the only computer which cannot be joined to the domain because of DNS error? If the answer is yes, right click network places (on the winpro system) right click Local ARea connection go to TCP/IP configuration, click properties, check if the system has a different entry for DNS IP address. If none try inputting the correct IP of the DNS Server.

If you require the system to obtain DNS server address automatically, then you have to configure in the DHCP Server, if one is present, theDNS IP Address. Go to MMC console, click on the DHCP, on the dropdown folder, right click Scope Option, Configure Options, Look for 006, check it enter the DNS Server Name then click resolve.

But if other clients were able to connect to the Domain without DNS issue, your DNS configuration at the DHCP lebel, scope options seems to be functioning.