I'm using Windows 8.1 and use save as. I don't know what you mean, duplicating at the OS level.
A week before I edited Halloween photos with Photoshop cs5 and had no problems. A few days ago, I was editing wedding photos and saved them the same way I did the ones from Halloween. I use the same name and just put ed in front of the name to save. Well, at some point all the names were the same except for a number (edxxx (y).jpg). The y was different, but edxxx was the same for each photo. xxx was for some photo in the middle of my run of pictures.