Ok, I figured it out. If you have your folder view options set to hide filetype extentions, then even if you put .cfg at the end of a txt file, the actual name of the file will be ScienceDefs.cfg.txt, so what you need to do is this : open any folder. go to folder and search options (under organize in top left corner). under view options deselect "hide extensions for known file types". now go to the file you want to change it will be say "suchansuch.txt" change last three letters making it "suchansuch.cfg" I just did that, and the name of my file suddenly showed as ScienceDefs.cfg.txt, so now I can just rename it properly, and it will change the file type as well.