CloneSpy is a fast and capable tool which can help you to find and remove duplicate files.
And while that's probably the program's most common application, it can also look for files which aren't quite identical. You can have it search for files which are the same name, say, or the same name and a similar size, or even just zero length files, whatever they happen to be named.
This is perhaps a little trickier than it should be, thanks to CloneSpy's less than intuitive interface. The program displays two "pools" where you can add folders, for instance; it can run in "Pool 1 only", "Pool 2 only" or "Both pools" mode; and you can make or add CSC (checksum) files. What does all this mean? We didn't know at first, either, so expect to spend a while browsing the Help file (itself fairly complex) before you properly understand what's going on.
Other elements of CloneSpy are fairly straightforward, though. You can have the program automatically delete duplicates according to your preferred rule (older, newer, small, larger, longer name, shorter name, more) just by selecting it from a list, for instance.
And in our tests the program seemed to find duplicate files extremely quickly, maybe faster than anything else we've used.
But please note, as ever with this kind of tool, treat it with extreme caution: used carelessly it can trash your system to the point that Windows won't start again. Don't use CloneSpy unless you fully understand what you're doing, and you've a full and recent backup to hand.