[Roy Dennis]

I reckon you have duplicated Disc Id or Book Ids.

The first time you rebuilt the database did you get a message telling you this ?

If it finds duplicates it usually moves them to a quarantine folder.
It also usually suggests merging them.
Thist would be the easiest way to relocate them but will mess your previously printed songbooks up if you use Book Ids. Plus may end up different to your other computer.

Alternative 1: Do the files match the same file path as the old computer ?
If so replace the files in the quarantine folder to their original location then Replace the songs.mbd with the copy from your old computer, then start Hoster.
It might rebuild the database automatically in which case it will have failed and back were we started, If it starts as normal see how you get on with that but remember if you ever rebuild the database again you will be back with the same problem.
Alternative 2:
Much more work but will keep your songbooks correct without reprinting and still match your old computer and also be permanent and not mess up next time you rebuild. See if you can follow this.

To see if any have been moved to a quarantine folder use Windows search feature and just type quarantine, if it finds any open them to see if the missing files are there.

Also you can find details of build database errors by opening Tools/Hoster Data Folder and find 2 files one is BuildSongDBLog.txt the other is BuildSongErrors.txt Open them with notepad to read them but dont alter them for now.

Its no good just moving the quarantine files back until you know which file has a duplicated disc id or book id still in your database as until you remove that it will keep throwing the others out.

So after reading those two files, run through the IDs and search Hoster via those disc Ids and see if a different file comes up. You might find a single file has replaced a whole disc then you could delete that one file via the edit dialog, replace the kma from quarantine to their original place then rescan that folder again which should replace that Disc id correct.
The file you deleted because it had the same ID you would have to re index.
Alternative 3
Another easier way.
You have probably told me before but I cant remember, the computer that you copied the KMA files from before they went missing, what version was it ?

If it has the Backup/Restore feature and the kma files follow the same path then create the backup and restore on the new computer, before starting Hoster move the files from quarantine back to their original location.