I own a C-200 mediaplayer, and I finally started organizing my music. I had to create a lot of playlists, and although the mediaplayer interface makes that possible, it isn't very handy if you've got a lot of files. I created a script for that.
the script creates a playlist for every sub-directory. So if you've got a directory named Beatles, and in there are some sub-directories, you'll get a playlist for every sub-directory and a playlist to play them all.
find . -type d |sort| while read -r DIR; do
find . -type f |egrep -i 'mp3|ogg|wav'|grep -iv playlist|sort> '00-Playlist.m3u'
chown nmt:nmt '00-Playlist.m3u'
Execute this on the command-line of the C-200, in the right directory (in my case it's /opt/sybhttpd/localhost.drives/SATA_DISK/Music for the default directory of the built-in harddisk). The chosen name makes it appear as first in the list of files.