I used my mz-nh1 to record a 80min MD with ATRAC & ATRAC3 codec music files. But when I inserted the MD in my mz-1 I just heard a long "beep" and the screen showed Hi-MD. I'm pretty sure it's just a regular 80min MD. So, why my mz-1 couldn't play it. Because it's a 80min MD? What type of music file can be played on mz-1?