You MUST retain no less than 2 backups at all times. Removing backup history to a single backup file will give you an INVALID error message that will keep you from recovering your data. I did numerous tests after I lost the ability to restore my data when I reformatted my HD.

Looking at the dates of the files, it appears that the history can span between more than one backup. Removing history is fine AFTER you have successfully restored data and not before.

Viwiz, the simplest solution is to allow Ghost to manage the deletion of the oldest backups automatically.  See Step 12 on page 51 and pages 78+ in the Norton Ghost 10 User's Guide for further information.