the unfortunate problems with proprietary formats are:
- they are likely to have copy protection included too
- since it is proprietary, the chances of the company releasing any information on how to convert the format to other formats are low to none. And if they don't give out such information, there is nothing anyone else can do about it.
Your only strategy here is to keep mp3 copies of all your files on your computer, so you never lose the original files after they have been transferred to the portable player.