Convert Primary Domain Controller to a Child Domain Controller.

Hello everyone -

I know that this probably isn't possible but asking never hurt.

We currently have a Primary Domain Controller for a single company
network. We're looking to move to a more Enterprise level layout and
have a Parent Domain, and have 3 child domains.

Two of the child domains will be completely new build servers so adding
them to the new Enterprise-level Parent Domain won't be difficult.
However, there is 1 PDC that has a very elaborate Active Directory
structure that needs to be placed under the new Enterprise PDC.

>From my knowledge of Active Directory, it doesn't seem like one can
demote a PDC to a child domain without completely rebuilding the
server.

I was wondering if anyone out there knew of another way.