I'm sure I sound like an idiot, but...

I need to install CRM into the following environment and have some
trepidation about it:

Domain A - server 1 is Win2k3 Server with SQL Server is the domain
controller. Server 2 is Win2k3, Exchange 2k server (yes, allready the
trouble begins) and proposed CRM server.

Domain A currently runs in mixed mode because -

Domain B is a Win2K Domain and Domain C a WinNT4 Domain and both have
external two way trusts with Domain A and I suppose each other?

Unless I'm looking at the wrong type of info, if I raise function level
on domain A to native mode to install CRM, I lose functionality on NT
and with Win2k3 Interim, Win2k. Or is that totally unrelated to a
simple trust?

Users have all been migrated to Domain A and as far as I can tell,
Domain B and C are there to support legacy systems. Unfortunately,
I'm not sure I have the whole picture from the client and I'm
afraid that what I can't infer about the situation is going to get
me.

I'll be reading up on AD and domains if anyone has a chance to offer
any insight, I'd greatly appreciate it.

Regards,
Bryan