A. A. Unlike earlier versions of Windows NT, the role of a server can be changed at any time in its life, e.g. from a member server to a domain controller, and from a domain controller back to a member server. This means that when initially installed, ALL servers are installed as stand-alone/member servers (even upgraded PDC/BDC's) which then have to be promoted to domain servers.
For information on promoting a server to a domain controller see Q. How do I promote a server to a domain controller?