For many different deployments, upgrading versus migrating is indicated by the deployment goals and contingencies of the existing server and network operating system (NOS) infrastructure.
The decision whether to migrate or upgrade depends upon a number of factors. Start by answering the fundamental questions for each server:
Is it possible? Do the system hardware and software support an upgrade, and, if so, to which edition of Windows Server 2003?
Can the existing hardware support the necessary service and operations load?
Is it desirable? Are there services or applications that are beneficial to maintain in place, or would you be better off with a new, clean installation and migrating the data?
When installing Windows ...