Any image-based snapshot tool requires extra setup if Exchange or Active Directory is involved.
For Exchange, you have to enable the Exchange VSS writer (disabled by default on SBS 2003). That and other tips in this post in the StorageCraft ShadowProtect forum.
Active Directory Backup
And this little surprise is buried deep within MSKB 888794, Considerations when hosting Active Directory domain controller in virtual hosting environments: restore of Active Directory is only supported from a System State backup. “In particular, Active Directory does not support any method that restores a snapshot of the operating system or the volume the operating system resides on. This kind of method causes an update sequence number (USN) rollback. When a USN rollback occurs, the replication partners of the incorrectly restored domain controller may have inconsistent objects in their Active Directory databases. In this situation, you cannot make these objects consistent.”
The explanation makes it sound like there is only a risk if you do replication, so if you only have one domain controller (no replication) you might get away with it. But it’s probably better to do a System State backup using a traditional backup tool regardless.