ESENT Event ID 215 - Certsrv.exe

Backup fails on a computer running SBS 2003 -

To resolve this problem, re-register the Sqlvdi.dll file. To do so, follow these steps:

1. Stop SQL Server.
2. Click Start, click Run, type Regsvr32 Path\SQLVDI.DLL in the Open box, and then click OK. The default path of the Sqlvdi.dll file is C:\Program Files\Microsoft SQL Server\80\COM.
3. Restart SQL Server.

http://support.microsoft.com/kb/830575