Microsoft replaced NTBackup.exe with wbadmin in Windows Server 2008. My first brush with this new program came with a necessary System State Backup prior to applying a schema mod to our Test Forest this morning. Our Test Forest runs on virtual machines (Hyper-V), and we haven't been building these VMs with more than a system volume to date. This came back to bite me this morning... First I attempted to take System State Backup to a network drive, then to the local system volume. Here's the output...
C:\Windows\system32>wbadmin start systemstatebackup -backuptarget: \\server\share.
wbadmin 1.0 - Backup command-line tool
(C) Copyright 2004 Microsoft Corp.
Starting System State Backup [6/16/2008 10:10 AM]
Retrieving volume information...
This would backup the system state from volume(s) Local Disk(C:) to \\server\share. Do you want to start the backup operation?
[Y] Yes [N] No y
Creating a system state backup to a shared network folder is not allowed. To store a system state backup on a shared network folder, first run the backup to a local volume and then copy the backup to the shared network folder.
C:\Windows\system32>wbadmin start systemstatebackup -backuptarget:c:
wbadmin 1.0 - Backup command-line tool
(C) Copyright 2004 Microsoft Corp.
Starting System State Backup [6/16/2008 10:18 AM]
Retrieving volume information...
This would backup the system state from volume(s) Local Disk(C:) to c:. Do you want to start the backup operation?
[Y] Yes [N] No y
ERROR - The location for backup is a critical volume.
Good times... Turns out that Microsoft disabled the ability to save System State backups to the system volume (termed a "critical" volume here). There is a fix for this in the form of a registry change. The article is located here: http://support.microsoft.com/kb/944530. Note that to implement this change, you will need to create a new key under the HKLM\System\CurrentControlSet\Services\wbengine, as well as adding the necessary entry. Simply adding the entry to the existing key will NOT achieve the desired behavior.
PS: Here's a spot on look at AD Backup and Restore in Server 2008: http://technet.microsoft.com/en-us/magazine/cc462796(TechNet.10).aspx