Backup Problem (Volume Shadow Copy)

I am trying to backup some data in my PC. I tried the HDD
on my PC for storing the backup and also the USB HDD i
have but got the same problem as follows:

"
Backup Status
Operation: Backup
Active backup destination: File
Media name: "Backup.bkf created 5/21/2004 at 6:39 PM"


Error returned while creating the volume shadow
copy:80042301
Aborting Backup.

----------------------

The operation did not successfully complete.

----------------------
"

Please any remedy...

thanx