A. Server 2008 introduced Windows Server Backup to replace NTBackup. Windows Server Backup does away with tape-target backups and instead creates volume-level snapshots to .vhd files. However, Windows Server Backup doesn't support the Exchange Extensible Storage Engine (ESE) streaming backup APIs, which means that Windows Server Backup can't back up Exchange. Note that Windows Small Business Server 2008 can back up Exchange.
To back up Exchange 2007, Microsoft recommends that you use a third-party backup application that supports the Exchange 2007 ESE streaming APIs or a Microsoft Volume Shadow Copy Service (VSS)-type backup solution that supports Exchange-aware VSS-based backups, such as Microsoft System Center Data Protection Manager (DPM) 2007.
The good news is that Microsoft received a lot of negative feedback about this lack of native backup support for its own product. So, in June 2008, Microsoft announced that it's working on a VSS-based plug-in for Server 2008 Windows Server Backup, which will enable Server 2008 to back up Exchange 2007. When the plug-in is released, I'll post an FAQ about its use and where to obtain it.