[Roy Dennis]

When you say you delete a folder are you doing this in windows explorer or through the Hoster program ?

To remove a folder from Hoster build database dialog you would choose "Exclude folder" button it would then remove that folder from the songs database, to reimport it you would first have to select view the Excluded folders by pressing that button then select the folder again then press the remove folder from list button in that dialog to allow it to be reimported.

If you delete a folder in Windows Explorer then Hoster still thinks it's in it's database so will think it is seeing a duplicated file.
So if you do delete the file in explorer you should rebuild Hosters database straight afterwards, it will then clear those missing songs from it's database.

Also as you have two computers one as a backup are you inclined to sometimes add new songs on one then next time add new songs on the other, this can also cause conflicts with bookids, best to always use one computer for newly imported songs. Then either just add the new folder to the backup machine or if it's new songs in an existing folder just use the rescan folder button to add the extra songs.

If you are missing songs I should also check the Quarantine folder, if you find any in there you should be able to copy them back to their original folders.