Group policy - settings been overwritten

[merreckB]

I have my DC default group policy and a policy on OUtest which contains 2 W2K servers (A and B). My DC's are 2000 also.
How do I have it so that the policies I set in the DC policy and the OUtest policy merge together?
On the DC GP I have the 'Logon as a service' (for example)and assigned that to the xxxgroup and the yyygroup. On the OUtest GP, I have the same service but I also want to have

http://WWWgroup

to have that right.
However, when I check on the server A, it only has the

http://WWW group

assigned. The OUtest GP overwrites the DC GP.
How can I have it so that both policies apply and the DC GP is not overwritten?
I have used the No overwrite option but maybe I am using it wrong.
Thanks in advance.