[MRM66]

Originally Posted by chaley

As you keep coming back to this I suspect you really do want to get rid of at least some of them.

I would delete the ORIG formats. The easiest way to do that is:

1. Make a backup of your library in case something goes wrong.
2. Open the "Formats" section of the tag browser (the pane on the left).
   Attachment 209015
   
3. Click the ORIG format you want to remove. A green plus sign will appear and all books having that format will be listed in the book list.
   Attachment 209016
   
4. Press CTRL-A to select all the books.
5. Right click on the ORIG format and select "Remove ORIG ...". In this example it is "Remove the ORIGINAL_EPUB" from selected books".
   Attachment 209017
   
6. Answer the "Are you sure" question.
   Attachment 209018
   
7. The format is deleted.
   Attachment 209019

Note: while preparing this post I found a bug in the current calibre version where the tag browser formats list isn't cleaned up after deleting formats. I submitted a fix to Kovid for the next release. In the meantime you can "force" a cleanup by typing E (for edit metadata) then immediately pressing OK.

EDIT: The fix is now in calibre source and will be in the next release/preview.

Thanks
Got halfway and chickened out lol
I seem to have 2 Formats Lists to pick from.
When I add a book to calibre I add all the details
Edit Metadata
Custom Metadata
Formats

So some are still saying Epub.Mobi in the box there. Most of my 4000 books
Too many to type te change to just EPub