Take my advice from yesterday and your problem will be solved.
Your phone supports mp3 files. Not DRM'd AAC or DRM'd WMA. Just mp3. Your Napster files are DRM'd WMA. That is why disc2phone won't let you add those files to your phone. On the Napster front page is says "...you can fill and refill any compatible MP3 player without paying per song". Note the keyword 'compatible'. Your phone is not compatible.
You need to
convert your files to mp3's.