Hi Brian
Have you tried to setup each client computer using the wizard? Go to the Win2K server and click on Start>Small Business Server Administrator Consol. This will dispaly a consol with two panes. In the left pane select computers and you should see a graphic near the top of the right hand pane labelled 'Setup Client Computer' Click on this and follow the prompts. You must enter the computer name exactly as it is on the client computer - right-click My Computer, select properties and then click the Computer Name tab to view this on the client. The wizard will prompt you for a floppy disk onto which it copies four files, one of which is setup.exe, which you should then run on the client in question.
Also, you must make sure that the DNS server adress(es) are listed correctly. For example clients have 192.168.0.1 as the first IP address on my network to search for when registering on the domain, a second DNS address points them to the router (or the machine acting as the internet gateway). This second address is the same as the gateway address (otherwise the client will query your internal DNS server when trying to resolve internet addresses and fail).
You must also make sure that the clients are configured to get their IP addresses dynamically if you are using DHCP (though the network setup disk should do this for you).
Check your server to make sure that the DNS server service is running, and make sure it is configured correctly. You must also make sure that the DHCP server service is running, and that the service is correctly configured.
Hope this helps