Something that may help. There is a free program out there called VisiPics (no link needed, just Google it) which will go thru a folder (and all the sub-folders) and find all duplicates, irregardless of their size or filename. How well it does depends on how tightly you set the search parameters. You can then mark the duplicates to be removed or to move them to another folder.
Be forewarned: unless set on the tightest setting, it will consider pics with slight varations (such as a moved arm or leg) to be the same pic. You can look over the found dupes by mousing over each thumbnail and it will show you a bigger pic.
Hard to beat for the price (free).