second domain in tree

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

I have a Win 2000 domain upgraded from NT, still running in mixed mode -
mycompany.priv. This domain has trust relationship with an NT 4.0 domain
called automation. I have a DNS entry pointing to the automation domain PDC
(only one controller - I have a current image saved) in mycompany.priv DNS
server. The NT PDC is pointing to mycompany.priv DNS servers for name
resolution and Internet access. The automation domain is on a separate
subnet and uses more protocols that my main domain/network. The automation
users are really in both domains: they have a regular AD account in
mydomain.priv and Exchange 5.5 account, they also have user names in
automation (NT) domain, that are identical to their AD accounts. These
users use resources in mydomain.priv, and their NT accounts are secondary on
their Exchange mailboxes, so they can log into their mailbox from both
domains. The machines in automation (NT) domain are majority NT (because
some automation/controls software will not run on Win2k).

I need to upgrade the NT domain to Win2k and switch both domains to native
mode, and retain trust, of course. What's the best way to do it? The
automation guys were separate because they wanted to control their
addressing, accounts, resources themselves because of testing.

I assume that I will stay with a separate domain for automation
(automation.local) in mydomain.priv tree. What about DNS - should I put a
dns on automation or I can use DNS servers from mydomain.priv? What's the
best order of operations here?

Help greatly appreciated. My first upgrade from NT (mydomain.com) was
almost flawless and everything has been running fine for 4 months. I am in
the process moving file servers from Netware to Win2k3 so it would help if
the Automation upgrade worked the first time without adding to my
workload -).