A. When you add a new DC to an existing domain, the new DC typically receives all Active Directory (AD) content from an existing DC on the network. This process can take some time, especially over slow network connections or on very large domains.
With Windows 2003, you can optionally install a new DC to an existing domain using a system-state backup of an existing DC from the same domain. (You can't use this method to create new domains, however.) The DC backup can reside on CD-ROM, DVD, or a local disk.
Keep in mind that the DC backup must be within the tombstone lifetime of the domain (typically 60 days) and that some replication with DCs will still take place (i.e., to get updates since the backup was taken and updates to the SYSVOL share content).