you have to put it back in unit that created the cd and 'finalize' it. this will make it readable to other playback units

 

So your friend made you the disk? He used a program to change the format to play on your radio. that was thee point I made he had to use real player to change format. Think of it as trying to play a Blue Ray disc in a DVD player.

 

I think miami touched on a critical point of making sure you finalize the disc. The one my friend made for me was indeed MP3 and had 93 songs on it. Played in my stock HU with no problems.