finding files under 1 folder absent in another

[robirdman]

I mixed up an archive hard drive with one that I used to duplicate the former.

Stored are thousands of digital camera images.

Normally I use Retrospect to duplicate the contents of one to its backup. this adds new files and deletes ones that are deleted on the archive.

Since I screwed up at some unknown point, I started adding recent images to the wrong disk, the backup, so if I duplicated the archive now, I would overwrite images on the backup that aren't on it, totally losing them.

The images would be scattered in subfolders of subfolders etc.

Is there something like that which exists in MS Access, to list the files that are in one and not the other?

Just creating 2 windows or the 2 drives and comparing all the files in all the multi-subfolders would be take many hours.