I think Kovid made libprs500's command line utility more powerful than the GUI version on purpose. ;-) Type the following in a terminal window:
Code:
prs500 rm /Data/media/audio/filename.mp3
and substitute "filename.mp3" with the name of the file you want to delete.
You can also type
Code:
prs500 ls /Data/media/audio/
to get a listing of the files in the directory. This works, as far as I know, for the "audio," "books," and "images" directories.
You can also copy your own content the same way you deleted the files by substituting "cp" for "rm." Something like:
Code:
prs500 cp /home/beartard/music/mysong.mp3 prs500:/Data/media/audio/mysong.mp3