Sorry, I don't think I explained myself very well, this time, I gave you half the required information but not all of it, sorry.
The importing is as I described, but if you find the song you want to convert and right (control) click on it then you can convert the file to the format that importing is setup for, which as you have now set it to import as MP3 will enable you to convert songs to MP3, then you can import the new MP3 version into powerpoint, making sure you delete it after you've done the presentation, it's a duplicate and will be lower quality after all.