deleting a domain

On a separate server, I have setup an experimental domain to test new software, etc. I want this domain to be completely unassociated with the network domain. On both domains, I’m using NT Server 4.0. Neither domain trusts the other and when I logon to the experimental domain, I am given the experimental domain’s name as the only domain choice. However, when I am on the PDC of our network domain or at any PC on the network, when I go into NetNeigh>Entire Network>MS Windows Network, I am able to see the experimental domain.

How do I delete/remove this experimental domain from our network domain?? Any suggetions would be greatly appreciated. Thank you.