[Micrus]

Если просто грохнуть рутовый домен, то у тебя не будет Shema master and Domain naming master
Соответственно у тебя не кому будет выполнять эти роли.

The schema master performs the following roles:
! Controls all originating updates to the schema
! Contains the master list of object classes and attributes that are used to
create all Active Directory objects
! Replicates updates to the Active Directory schema to all domain controllers
in the forest by using standard replication of the schema partition
! Allows only the members of the Schema Admins group to modify the
schema
Each forest has only one schema master.

The domain naming master controls the addition or removal of domains in the
forest. There is only one domain naming master in each forest.