Win 2000 server domain problem

My office have a active directory and domain controller running on window 2000 server

All of the old computer also joinned domain and staff can use their domain account to login in the domain smoothly.

But the problem is when have a new computer need to join domain. That will have a error message the meaning about cannot find the domain.
For example, My company have a new computer now. The OS is win XP Pro. I want to put this computer to join my company domain. My company domain is jjhg.com. But when I use jjhg.com try to join domain. That will have a error message like cannot find domain “jjhg.com”.
How can I solve this problem?
Thank you!