If you have bought the FFVI soundtrack or if you have downloaded some FFVI mp3s or midis you should know that there is a track called "??" (two qustion marks). Whenever I try to rename that track into "??.mid" it says that you shouldn't have the following signs in the file name:
/ : * ? " < > and some other...
So, how have you done. What is the file name of that track in your computer?