Active Directory Domains and Trusts Snap-in (domain.msc)
Tasks that can be accomplished:
Raise domain mode (Windows 2000) or functional level (Windows Server 2003) of a domain or forest, manage trusts, and view and modify the description and managedBy attributes for a domain
Type of tool:
MMC snap-in
Where to find it:
adminpak.msi for Windows 2000 and Windows Server 2003