Humm maybe theres another way to explain
Music on computer in folders. (A albums in A folder, B albums in B folder e.t.c.)
Add music to windows media player library.
Songs or ablums on computer has an apostraphe(') or ampersand(&) in its actual file name.
Create windows media playlist of favourite songs.
All albums in A and B folder for instance.
Save play list into Playlists folder in the same place as the music
i.e.
C:\A\Adele\track 1mp3
C:\A\Adele\track 2 & crazy.mp3
C:\Playlists\My favourites.wpl
Copy all of those files to a USB drive.
Insert into car, select the playlist called "My favourites.WPL".
All songs play apart from "track 2 & crazy.mp3"
I wonder why that is?

Looking inside the WPL file using notepad in windows it would seem that windows media player called it
<media src="..\A\Adele\track2 & crazy.mp3"/>
If you then modify it to
<media src="..\A\Adele\track2 & crazy.mp3"/>
It works wooo hooo.
I hope that makes more sense.