If it is an iPod the problem could be iTunes related.
iTunes tries (and often fails) to sort files in some logical order.
The intention is to group files together by artist (or performer).
A side effect of this can often be a CD gets ripped but then split apart because not all tracks are performed by the same artist.
'Greatest hits' albums are particularly vulnerable as some tracks may be performed by the band/group/orchestra while others may be solo tracks (and get split apart from the rest).
Compilations can do the same thing.
iTunes also gets completely confused when albums have the same title.
The work-around is to view how the tracks look in iTunes before syncing with the iPod (viewing the list as "albums by artist").
Tracks can be moved around and grouped together, albums can be renamed (so there aren't duplicate names) and tracks can be moved from one "album" to another.
This is best done after each CD is ripped (because it's a pain in the butt when the iPod or iTunes folders is fully loaded).
If your friend doesn't have an iPod, and has another type of music player (he does, after all say "on my MP3"), it'll probably be how he's grouped the folders - if all tracks are in the same folder (on the MP3 player), the player itself will be trying to sort them. If you manually put them in separate folders the order will stay sensible.
ADSL2+ with BE
DL Sync around 4.8Mbps
UL Sync 1088kbps
DG834GT with DGTeam firmware