Re: duplicate files
There are tons of programs (freeware and shareware) that describe themselves as duplicate file finders or deleters or managers.
But I think that not all of them have the option to handle more than 1 drive at the same time, so that would be a nice selection criterium when you start selecting, downloading and trying them. Then choose the one you like most.
I'd start with our download.com, but there are other trusted download sites also, like tucows.