[Roy Dennis]

If you just Add the folders to the rebuild list I think you will just get another load of duplicate book id's again so I would import them again from scratch from the import song files dialog.
Before attempting this open the folder in Windows explorer and delete the "ImportedFiles.txt" files important. You can also delete any other .txt files in this folder and all the .kmh files so you are only left with the original zip file or if they are mp3+g the mp3 and the cdg file.
This can be made easier by right clicking in the folder and select sort by Type, if type is not showing select More then tick the box for type then that option should appear.
Now you need to open the Build database dialog, select the excluded folders button, select the folder in question and remove from list to allow it to be imported again.
Now use the index songs files button to open the Import Hard drive files dialog on the actual computer your having the problem with. Depending on the way your files are named it could be best to set the field separators to ignore the Disc Id and track # unless you specifically want that info imported, this will allow the full 99 tracks per book id and avoid any conflict if the files in this folder have an identical disk Id to those you already have imported.

The problem with importing from different computers arises when you import some files one week on one computer, then another time choose to import on the other computer, if you were to stick to the same computer every time the problem would be unlikely to occur.

When you import songs Hoster allocates a book Id and a disc id if one is not entered. So if you were starting from scratch the first book Id would be 101 which would be disc 1 track 01. Now after many imports you may have 50101 (Disc501 Tr 01) now if you get another computer and you import a new disc in it and import it will be given the 101 number, so if you then try to copy this already imported file to the other computer it sees it as a duplicated. You can set a higher number than the one allocated when importing where you see the next button but you can still get a problem with disc id numbers if they end up the same.