Rick,
the settings you are referring to reside in the Computer
Configuration\Administrative Templates\Network\DNS Client group policy node
("Connection-Specific DNS Suffix" and "Register DNS records with
connection-specific DNS suffix"). Note that these require XP Pro clients and
will apply across all connections on multihomed computers.
Could you clarify what's the primary DNS suffix on your clients? By default,
this should match your domain name and should be used by your clients for
both DNS name registration and resolution...

hth
Marcin