Thanks, all, for responding.
To clarify somewhat, based on your responses:
@itimpi: I was trying to copy/paste the whole calibre directory - not individual files. Because of the warning elsewhere, I specifically made sure that the destination path was shorter than the source path.
Thank you - I'll "bug" the other issue.
@user_none: I'm not quite sore what you are suggesting, but if I read you correctly, the problem includes the fact that I can't see ther files, nor their directories - either Book or Author, in Windows Explorer, so I can't navigate to them.
@theducks: All of this occurred from within a Windows 7 environment. None of these files have been exposed to any other environment while they have been in my posession.
I'll try to use xcopy to copy the lot, and see how many turn up in the target directory.
@kovidgoyal: There is no issue with DRM here for any of these publications. Oops - that was so high, I mistook it for your response
. I wonder if perhaps the problem is to do with the whole directory being moved AFTER it has been created, resulting in longer file name paths? Is there any tool that can run through the structure to make sure that there are no suddenly created long file names? And no - because Windows Explorer doesn't even realise that these files exist, I can't copy them to a shorter directory structure. I could try shortening the existing structure temporarily to see if any currently missing files suddenly reappear - that would tend to prove / disprove that I am looking at a file name length problem.
Thanks, all - I'll get back to you if I find out what's happened - in the mean time, if any one else has any clues as to what is going on here, I'd appreciate any help that I can get.