Error Returned While Creating The Volume Shadow Copy How Do I Back Up My Computer When I Get This Error?

How do I back up my computer when I get this error? - error returned while creating the volume shadow copy

The error report says ...

State Backup
Operation: Backup
Active backup destination: File
Media name: "April 11 backup 2009.bkf created 4/12/2009 at 4:14 pm"


Error while creating the volume identified: 800423f4
Abort backup.

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The operation fails.

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This is the backup file from Windows!