Can you check that you are trying to continue the earlier backup schedule to the new hard drive? If so, the backup service may still look for configuration files in the new hard drive location (may be at WindowsBackup folder in the drive root directory).
You may get this issue because of these files are not available.
To fix this, you may need to schedule a new full backup to the new hard disk OR delete the previous backup and create a new backup schedule to the new hard disk. Also, don't forget to delete the log of previous backup schedule from the server admin console.
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Aravind
www.vembu.com