Great to see you rediscover how this works! Note that tape file names on MSX can only have 6 characters and extensions are not used (because they also use part of the 6 characters as you saw). To load you can also just type CLOAD and the MSX will load the first program it will find. By the way, perhaps the above comment was already made, but I haven't tried to Google Translate all the Japanese comments, sorry about that.