To start with a clean Windows Backup Logs and Catalog, (usually when a Backup Disk has failed and not longer usable).
- To remove the Catalog run: wbadmin delete catalog
- Remove the logs, In the Eventviewer – Applications and Services – Microsoft – Windows – Backup, right click on Operational and select Clear Log
The above will completely remove your Backups so should only do this if those backups are no longer required.
We would always recommend offsite backup and not to USB Hard Drives as they are prone to failure