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In Windows XP the file extension gets selected when renaming a file. If I choose to add that extension to the Known filetypes, it doesn't show the extension but the file type still changes.
For example, whenever I rename a subtitle (and I do that very often, because I use Serviio), I can edit the whole name (Subtitle name and the".srt" extension), not only the name. I have seen similar posts, but none worked, I even tried the "The End" program, and nothing.