Hello,
Assumption : Backup Exec is installed on the domain Controller which you are trying to restore. Hard Drive has not gone bad, the server is up and running, but we only need to restore the AD Database
As the AD Database is down in DSRM, there is no one to authonticate the BE service account.
1 : Start the Server in DSRM
2 : Open the services console and change the startup type of all the Backup Exec services to Lacal System.
3 : Open Backup Exec and perform restore of the C-Drive, system State and Shadow Copy Components.
http://seer.entsupport.symantec.com/docs/236240.htm
Senario 2:
The Hard Drive of the Domain Controller gone bad
If you are facing the 2nd senario, please let me know