Sorry. Googled and found no help. I can see that they are new game formats. But I downloaded one or two that I found and had no problem (same name) copying to the same folder. Wild thought - I wonder if your antivirus isn't messing with them in some way?
What's strange to me is that you can't see the file extension even though you have 'hide known extensions' unchecked. I suspect that this is what you should be looking into. If the extension is not being applied to the file name, you won't be able to name both files the same. Go to the CMD window and check the file names via dir.
I've seen this happen at times when working in Photoshop.
I just tried it and I was able to save the same file with the same name as .jpg, .psd and .png format with no problems.
But I have had times when it would rename files either Sprite (copy).xxx or Sprite (1).xxx.
I have never really thought about why it was doing this or that it wasn't the usual behavior.
Try and pick some other file and place it in a folder, i.e. a .jpg file and then save it again with another extension in the same folder i.e. .tif and see if this happens.
Determine if what you are observing happens with all files, or just the ones with the particular extension you are working with.
You should be able to see all the extensions for all the file types, if you can't there is some kind of error that should be addressed.
I did find someone who can't get rid of the file extensions... they received this information.
The "Hide extensions for known file types" option only applies to file types that are registered on the system.
If you have not installed the program that uses this file type, this could be the source of the problem that you are seeing.
Try installing that program that uses those files and this should register that .pes file extension.