Hi,
I have just managed to solve this problem! I had this problem after the HDD in my Synology NAS drive failed. Luckily was able to retrieve my files by creating a bootable USB drive with Ubuntu (there's a youtube video by techwiztime on this), and copied all my files onto the HDD in my PC.
Whereon I found tends of thousands of @eadir folders which I could not delete. I tried everything I could find in various forum threads, but Windows just will not find the files/folders. Even though it's displaying them in Explorer (turns out there are files in the subfolders with funny names that Windows and DOS don't like.)
Solution: I guessed that if the files were created by the Linux OS in the NAS drive, then I should be able to find - and delete - them using Linux, so... with the offending drive connected to your PC boot up Ubuntu, use Ubuntu's file explorer and simply search for "@eadir" and delete them all in one go from there. I've booted back up into Windows and the folders (and all the files in them) are indeed gone. Fuck yeah! 🙂
Now to buy a new HDD for my NAS drive...