Recovering Active Directory
After the domain controller is repaired, it needs to be restored with Active Directory.
Replication. If there is more than one domain controller in a domain, Active Directory is restored through normal replication with the replication partners.
Ntbackup Backup and Restore Wizards. Use the Ntbackup tool to restore the System State from a backup copy, which recovers Active Directory, FRS (including SYSVOL), and Certificate Services (if installed). This option is appropriate if there are no other domain controllers in the domain with which the domain controller can replicate.
In cases where Active Directory needs to be recovered from hardware failure or replacement where data on other domain controllers is known to be stable, you need to perform only a nonauthoritative restore from the most recent backup. After the nonauthoritative restore, Active Directory replication automatically begins propagating any changes from other domain controllers that occurred after the time of the backup.