can't see 90% of total music

 I  transferred +/-200 songs on my sansa clip zip, but after disconnecting and refreshing, I can only see around 20 songs in any folders of the sansa clip. I tried a few times (format and transferred again) and it always shows only the same 20 songs. It’s all mp3s that I use to listen on that player. When I look trough my PC I can see they are in the sansa player. It’s like it cannot recognize the songs.

Are you mp3 files properly tagged? They should be tagged in the MP3 V2.3 ISO 8859-1 format. Songs that aren’t properly tagged are probably showing up on your player as unknown. The free program mp3Tag makes it easy to modify many tags at a time.