I probably should have left all that "GC" "DC" "IF" talk out of the discussion, but since you ask...

The DC is simply the domain controller in a Windows 2000 domain. It replaces the old PDC (primary domain controller) model from the NT4 days. No more BDC's (backup domain controllers); all domain controllers are basically on an even playing field know as a multi-master model.

The GC is just a DC with the role of global catalog. IF master is the DC with the role of infrastructure master, and there are other roles as well. Bored yet? [Smile]