Windows 2000 DHCP includes a feature that prevents setting up "rogue" DHCP servers. If you have an Active Directory domain, the most likely cause of the problem is a failure to authorize the DHCP server.
In the DHCP Management console, right-click the server icon and select Authorize from the flyout menu. This puts a special object in Active Directory. The DHCP server checks for the existence of this object before enabling the scopes.
If you have authorized the server, or you do not have an Active Directory domain, then you might have neglected to active the scope. Right-click the scope and select Activate from the flyout menu.
This was first published in June 2001