Logging into Win2000 Srv from NT.40 Wkst

Hi,
Win2k uses DNS for name resolution. NT uses WINS. Install the WINS service on your Win2k server and your NT workstations will connect fine.
Hope This helps
Pete

Wait: you were running Small Business Server as your PDC, and you had NT4 Workstations as domain clients? Is that right?
Now you have installed Win2K? Ok.
First question: when you installed Win2K as a Domain Controller (there are no Primary/Backups in Win2K) did you run the Domain Controller program (DCPROMO) or did the install of Win2K ask you if you wanted it to be a Domain Controller? It sound like it did, but I want to make sure. Well, during this Domain Controller install, it would have asked you if there are going to be only Windows 2000 clients attaching to the network, OR will there be pre-2000 clients. What option did you select? If you chose the 2000 clients only option, then the PDC Emulator role was not assigned to the Win2K server.
That might be your only problem here. The PDC Emulator role does just what its name suggests: the Win2K server ALSO acts like a PDC for the NT4 and earlier clients. The normal Win2K Domain Controller install will (I believe) let ONLY Windows 2000 Professional and Server clients to connect to a Domain Controller; NT4 and others won't attach.
So, go into Active Directory Sites and Services Manager MMC Snap-In, go to properties on your server, and check out the Roles it has assigned to it.
Here is a Technet article about the different Roles:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q197132
(please remove any spaces)

Hope this helps.