I got an instrumental sound track on my computer, but Windows Movie Maker does not detect its format.?

So I tried taking it to a converter, because I thought Windows Movie Maker did not support MP3 files. I tried changing it to WMA, but the converter said it did not know what format it was, when it was clearly MP3. It said it supported MP3 changes, too. The music is 'Lily Allen Everyone's Changing Instrumental Track'. It is 11,378 KB.