As Massimo says, you'll need to perform a System State backup and then cover that backup with Bacula.
The standard way of performing such a backup file-level backup of the system state on prior versions of Windows was to use
ntbackup to write out a BKF file with the system state and cover that file with backup.
Windows Server 2008 removes
ntbackup and adds the "Windows Backup" functionality. You can do a system state backup with
wbadmin start systemstatebackup -quiet -backuptarget:X:, replacing
X: with a destination volume. You'll get a folder hierarchy in that volume, "X:\WindowsImageBackup", that will contain the backup set.
Beware, though-- if you attempt the backup on to the "C:" volume you'll receive a "ERROR - The location for backup is a critical volume" in a stock W2K8 install. You can send the backup to some other volume or you can set a flag to work around this "feature". Microsoft has an article describing how to override this behavior, which basically amounts to creating a REG_DWORD value named "AllowSSBToAnyVolume" set to "1" at "HKLM\SYSTEM\CurrentControlSet\Services\wbengine\SystemStateBackup".