Reading your posts from the top, the main issue from what i can tell is that you lost cover-art associations after reinstalling windows.
Correct me if i'm wrong but with a ton of them called 'Unknown.jpg', even if MC did backup the coverart as you requested, how will it be possible to relink them again ?
Don't they need to be uniquely named if they all live on one massive directory.
I don't know about your database, but I have over twenty custom fields, and large amounts of custom data added to each of these. There is no way this could be stored in any of my files tags; Some of this could be stored in a MP3's ID3 tags, but there's no way to store tag data in many of the odder video formats, and even when there is, this doesn't correspond to what I want to store.
Not sure why you mentioned this wrt to your request as its to do with the library.
But we have something in common here
I don't update tags on my files at all (for reasons mentioned in earlier posts), relying entirely on the library to hold all relevant metadata. So no different to image or video files that don't support tagging, cept it applies to everything in my library. Done this for a cpl of yrs now and even tho i've been through countless crashes the data has always been good.
I have this theory that if MC crashes while its writing to file tags then the library can be left in an uncertain state as i 'think' it only updates in the library once the filiewrite completes. So if it gets interupted during a file tag write, then that entire field can go blank !!
dunno if this is currently the case but it happened with older versionsBut with no file tag updates, library updates are very quick, so if there is a crash, chances are it happens after the library has already been updated, ergo less corruption or only loss from the last library save, which kicks off fairly regularly. I mean the main library here.
That's why i like the fact the library backup is as small as it is.
..and of course i cannot rely on update library from tags.
So i save to mpl the album's details for every album in its own folder as an extra precaution.