The duplicate files are located in C/D folder called "Mutablebackup". You can't see it normally as it is hidden. Download TreeSize Free to view it.
In the TreeSize Free program, locate the file. Click the subfolders of Mutablebackup and set yourself as the owner on every single folder under it, not individual files. Folders will do as long as it's not Mutablebackup itself. After you set yourself as the owner, give yourself full access to these subfolders. Then you can delete the extra space that clutters up after installing/patching/leftover Uninstallment data from PSO2NA.
PS: You have to enable "Hidden Items". To do that, click "View" on "This PC" or as the oldies knows it, "My Documents".
Hope this helps.