For years I've used NTBackup to backup Exchange database files. This is no longer possible in Windows 2008. I used this to backup files to disk and then copy these to tape SAN. This is no longer possible on Exchange 2007 SP1 server on Windows 2008 because Windows 2008 has removed the option to take file based backups to disk. NTBackup is able to read and restore data from old backup sets, but is not be able to create new backups.
This is because Windows 2008 has a new Windows Backup utility that performs block-level backups using VSS and can only backup full volumes. Backups are created as an image of the original volumes using VHD files, with VSS used to track and store changes. This means that you cannot store backup sets on the same volume as the original data and that you need to choose an empty volume as the backup target.
When upgrading to Windows 2008 keep this in mind and look at other solutions to backup Exchange including using DPM. Some info on this:
Correction - Thanks to tr!!! The Exchange Team is working on a resolution to this. No date has been set yet but don't expect full parity with the experience with Windows 2003 and NTBackup. http://msexchangeteam.com/archive/2008/06/18/449031.aspx