Folder Permissions for Dropbox (_not_ the website) Revisited

In my original post for creating a dropbox [folder], the client wanted a user to be able to be able to drop-only files 9mostly Word) into the folder, yet still be able to browse the contents of the folder. I have set permissions as below:

administrator -- full control
everyone-allow -- List folder / read data
Create files / write data
everyone-deny -- Delete subfolder and files

I now observe an issue in which an unwitting user drags a file into the dropbox and tries to modify the file. Windows dialog says user is not allowed to do this. User tries to do a Save As... and POOF! the original file disappears! What causes this in Windows? How can I prevent it?

Thank you -Kellen

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