Originally Posted by Dullahir
Thanks for the excellent suggestions. However some of these won't work.
Also, I'm trying to find the dupes *before* sending them to Calibre, since sometimes books are renamed 'Sin and Seduction' 'Sin and Seduction (2)' which Calibre doesn't locate, neither does DoubleKiller.
Give the Find Duplicates plugin for Calibre a go. It might do what you want other then finding the dupes before loading into Calibre.