1. Open command box and type the following command “VSSAdmin list writers”

All VSS writers should be listed with “no error”
If a writer has an error you can repair the writer using the follwoing article.
Link : [1] http://techblog.wanierke.de/2009/02/13/howto-repair-vss-writers/

2. Check the “COM+” services.

There should be listed two “COM+” services in the “services.msc” SnapIn.

3. Check the “Volume Shadow Copy Service” status.

The status of this service should be “Started”.

4. Perform a test backup of the systemstat using “ntbackup”.

Open a command box and type the following command
“ntbackup.exe backup SYSTEMSTATE /f “C:\Systemstate_VSS_Test.bkf”
When the backup runs without any errors please delete this file afterwards “C:\Systemstate_VSS_Test.bkf”

5. Check the fragmentation of all disks.

Open a command box and type the following command to check if the drive needs to be defragment.
“defrag <VOLUME> -a”

If the drive is fragmented, please use the following command to defragment the drive.
“defrag <VOLUME> -f -v”

6. Check if there is enough free disk space on the volumes. There sould be at least 10% free disk space.

You can check the free disk space of the drives via the MMC SnapIn “diskmgmt.msc” ( Disk Management )

7. Check if Windows Server 2003 SP2 is already installed. This service pack contains some VSS hotfixes.

Install SP2 on the server.

8. Check if the latest VSS hotfix ( KB940349 ) is installed on the server.

Install the VSS Update KB940349 on the server.
Link : [2] http://www.microsoft.com/downloads/details.aspx?FamilyId=AE17B7EF-3C02-496A-BB46-770C04E42B5C&displaylang=en