Troubleshooter: Performing ForestPrep in a Child Domain

We're planning an Exchange Server 5.5­to­Exchange 2000 Server migration. After we migrate, our new domain structure will have a root domain and several children, one of which will contain the Exchange 2000 servers. Can we perform the ForestPrep operation from the domain controller (DC) of the child domain?

You must perform the ForestPrep operation in the domain in which the schema master Flexible Single-Master Operation (FSMO) role holder lives. By default, the first DC that you install in the root domain always holds the schema master, although you can transfer it to another system. If you want to run ForestPrep in the child domain, you must use the Ntdsutil utility to transfer the schema master role to the DC in the child domain before you run the Exchange installer. Remember to run DomainPrep in every child domain that might host mail-enabled objects, including distribution groups or contacts.