This Active Directory domain controller currently performs the infrastructure master role. If you remove Active Directory ...

This Active Directory domain controller currently performs the infrastructure master role. If you remove Active Directory Domain Services (AD DS) from this computer, clients in this domain might have difficulty locating objects in other domains. Before you continue, transfer the infrastructure master role to a domain controller that is not a global catalog server. If it is not possible to transfer the role, first remove AD DS from this computer, and then use Ntdsutil.exe to seize the role. Use Ntdsutil on the domain controller that you plan to seize the role to; if possible, use a recent replication partner in the same site as this domain controller.

For more information about transferring and seizing operations master roles, see article 255504 in the Microsoft Knowledge Base (http://go.microsoft.com/fwlink/?LinkId=80395).