Error:

CExBackup::backupService:HrESEBackupSetup: Error Number  0xc7fe1f45: Instance not found.

Cause:

The drive where the transaction log files are saved is full.

Resolution:

To resolve this issue, remove un-needed log files to another disk drive to free disk space.

Refer to the following Microsoft Knowledge Base article for instructions:
For more information, follow article number to view the article in the Microsoft Knowledge Base:

How to remove Exchange Server transaction log files:

http://support.microsoft.com/kb/240145