It should not be possible if your songs are imported with their Disc id's as original kma files as Hoster should recognize duplicate Disc Id's.
One thing I will say, in the list of folders in the rebuild dialog check you don't have any listed twice or a folder from a backup listed. This might quite possibly result in some duplicate songs especially if Hoster created it's own Disc ID Like xyzxxx.
Rebuilding the database will not alter any of the edited changes you made providing you made the edits using Hosters edit dialog as that stores all the changes in the headers of each song.
When you rebuild it reads these headers and stores that info in the songs.mdb.
However if you made edits to the database using access which only stores the changes in the songs.mdb and does not re-wright that back to the headers then you could loose some of the edits.
So if you used Hoster to make your edits you can delete your songs.mdb and rebuild it. But it should not be nessacery to delete it as rebuilding it will overwrite the existing. If you are talking about version 5.05 or 5.06, if you delete your songs.mdb then restart Hoster it should start rebuilding as you start Hoster so if you have all your music on an external drive be sure to have it connected before restarting it the first time.