[enuddleyarbl]

Assuming I can just rename the file extensions to xhtml (i.e., there's no structural change), I'll probably do that just to get rid of all the warnings.

As to the fonts, none are in the Fonts section and I can find no reference to them anywhere in the book. So, I have no idea where they might be used of if they're needed. But, considering that I automatically delete all fonts when I start editing a book, I guess it ought to be fine without them. I'll try deleting the encryption.xml and see what happens.

EDIT: after some cursory research, it looks like converting those files from html to xhtml isn't simply a matter of changing the extension. Some things I've found that would have to be checked in the files are 1) document type declaration, 2) xhtml namespace declaration, 3) make sure element and attribute names are all lowercase, 4) match start and end tags, 5) make sure things like <br> are <br/>, 6) set all required attributes (and they're in quotes), 7) make sure all elements and attributes are in the xhtml spec being used. Those don't necessarily require changes in the files, but I guess I'd have to check for them.

Also, I did delete that encryption.xml file and everything seems fine. Since I've converted other epub2s to epub3 without getting encryption.xml files there, I'd guess that one previously existed here, I deleted it when I started editing, and the conversion process found its initial existence somewhere and put it back. Deleting it again shouldn't be a problem now if it wasn't then.