This article explains in details how to restore System States only.
If the machine is a domain controller, boot into Directory Services Restore mode (F8 on boot, select Directory Services Restore mode)
If the machine is running Certificate Server, either reboot into Directory Services Restore Mode or manually stop the Certificate Server service.
If the cluster database is being restored stop the cluster service on all nodes except the node on which the restore will be performed. (Alternatively, select the 'Force cluster database restore' option on the restore options screen - not recommended unless the user is sure this is what he wants).
Tick System State
Choose the SYSVOL authority level on the restore options screen (non-authorative, authorative or Primary).
- A primary restore should only be used when all domain controllers have been lost and the domain is being completely re-created
- Active Directory and SYSVOL should be restored with matching authority.
Run the restore
If the machine is a domain controller and Active Directory is being authoritatively restored, before rebooting use the ntdsutil tool to mark the Active Directory database as authoritative (MS KB article 241594, http://support.microsoft.com/default.aspx?scid=kb;en-us;241594)