Changing DNS Root Domain Name

Archived from groups: microsoft.public.win2000.setup (More info?)

We have two Windows 2K Domains.... lets call them Domain A and Domain B.
Domain A has been in place for a while and is in Native Mode.... Domain B is
newly installed and in Mixed Mode. However when the 2 DC's and Member Server
in Domain B were built they were given the same DNS Root Domain name as
Domain A (i.e A.co.uk). Therefore when the users in Domain B try and connect
to the Exchange Server in Domain A they are prompted for logon details as we
are unable to setup a trust between the two Domains as Domain B does not
appear in the drop down list it just shows as A.co.uk. What I need to know
is ther any way to change the servers in Domain B to have a different DNS
Root Domain Name so we can setup a trust (other than a rebuild)? .... thanks
in advance.

Domain A only has the Exchange Server in it if it would be easier to merge
the two domains????