Okay Robert, I am going to keep trying to help. But there seems to be an understanding gap that we need to get over here, and that might take some effort.
I have been able to restore some of them from my spare drive but they are not completely correct. For example I had ten or so Chris Rea Albums and knew which ones were missing. So I deleted the files from my hard drive and copied and pasted them from the spare drive and it imported them again.
First, do something for me, or more correctly, don't do something. Never, ever, ever, ever delete any music files off a disk, then copy them back from another disk, to try to fix the problems you are seeing. Don't do it. Ever. You are just making things far, far worse. Really, I mean it.
I did try to use Restore to a recent backup but it only imported around 408 megs of music.
Did you restore the MC Library backup? Or did you restore a backup of your hard disk containing all your music files on it?
If the latter, as above, never, ever, ever do that again. Backups of your music files are required only to restore corrupted, damaged, or lost music files. They are not required to fix problems in the MC Library.
I cannot emphasise the above issue enough. When you first had this problem, had you explained it instead of asking how to do a specific task (renaming files on your hard disk), the whole problem could have been very easily fixed. Now that you have deleted files, uninstalled and reinstalled software, made lots of changes to your metadata and rekeyed a lot, the problem is far, far harder to fix.
You are not alone in the problem you had. Other people have had it, and it was an easy fix, if they hadn't broken other stuff before asking for help.
Now, some information sharing. I want to know if you understand this:
The MC Library is like the old style Index Cards in a physical library full of holds books.
Your music files are like the books. They have some information in them about what they are, plus hold the content itself.
Some information about the books is stored on the index cards.
Information in the books about the books can be copied to the Index Cards.
Information in the Index Cards about the books can be copied to the books as well.
The information that I'm talking about is the tags that are stored both in the MC Library and inside your audio files.
If you had such a library, and you copied all the information (tags) in the Index Cards (MC Library) to the books (Audio files), then if your Index Cards were destroyed, all you would need to do to recreated the Index File is copy the information (tags) from the books (audio files) back to a new set of Index Cards (MC Library).
You do not need to destroy the books (delete audio files) and get a new copy (restore a copy of files from a backup drive) of them to recreate the Index Cards. You never, ever, ever have to destroy the books in order to fix a problem with the Index Cards. That is what I mean above. Recreating the Index Cards by reading the information in the books is like re-importing your audio files, including the tags in the files. In both cases, with the books and your audio files,
this is the hard way to restore the information.Alternately, and even better, if you had made a copy of your Index Cards recently (MC Library backup), you could get that copy of the Index Cards (restore a MC Library backup) and use that. Your Index Cards (MC Library) might be a little out of date, but if your copy was recent (automatic MC Library backups happen about every two days), then not by much. The MC Library is stored by default in this directory on your PC: "C:\Users\[User ID]\Documents\JRiver\Media Center 21\Library Backups\". You can access the MC Library restore process via menu at the top of MC, under "File>Library>Restore library". You will see the backup function is there as well.
Now Robert, I am not trying to be condescending. Sorry if I sound like a jerk. But do you understand the above, and do you understand that deleting audio files and restoring them from a backup drive is not the way to fix problems in the MC Library?
If you do, we can move forward and try to get you back to where you were before the original problem happened.