In Windows 2000, DHCP option inheritances uses the following priority, from least specific to most specific:
Default or server option
A more specific option takes precedence. When you remove a more specific option, any less specific option normally takes effect, except in the case of DDNS settings.
The only way to clear DDNS options from a DHCP scope is to use Regedt32 to delete:
where <ScopeAddress> is the address of the scope.
Stop and restart the DHCP server service.