problem with authentication and adding a new user in computer

Hello guys,


I have a network windows 2000 server.

We have some station windows 2000 and XP professional

In my computer (windows XP professional) I am trying to add

a new user the steps:

Controle panel
   user account
      add
        user name
        domain


default user

after clicking the button conclude, I got the folling
message:

User cannot be add because it generates the following error:
fail in trust relation between the work station and primary domain

How to solve this?

Another problem that I am having it is that my computer and other
computers are losing the authentication in the server.