I've now tried this out. It does indeed do what I wanted (keep the unmodified original) and answers my first question. I'll still be interested...
OK. I'll try that and post again to give the results. Thanks for the help.
Thanks, MudCrab. It looks as though I can't safely delete any differential backups at all. Even if this is not a bug (as someone else suggested)...
I have made a full disk backup and 2 differential backups but just want to keep the original. Can I delete the differential files? Second...
Separate names with a comma.