How to turn on the Exchange writer for the Volume Shadow Copy service in Windows Small Business Server 2003

http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q838183

If you run or develop a third-party backup program that uses the Volume Shadow Copy service to back up Exchange Server 2003, you must turn on the Exchange writer in the registry.

Caution If you turn on the Exchange writer, the Backup utility cannot back up the Exchange information store and the system state at the same time. Turn on the Exchange writer only if you use a third-party backup solution, or if you want to back up the Exchange information store separately.