Backing up Active Directory with Veritas Backup Exec 9.1

Does anyone know how to back up your active directory with Veritas Backup Exec version 9.1? I recently started working for a company the does tape backup of all their servers but they are not sure how to back up AD. I have never used this software to back up any servers as a matter of fact I have never done any server back up, this is my first. All servers have full weekly backups and daily differetial backups scheduled. I do not know where AD is located but I can find out. The operating system is Windows XP. Veritas has a ‘Job Setup’ option but you are not able to check the boxes for the users. All boxes are faded out. Can anyone help. Thanks.

-Alex