Good morning Ruivar,
Try starting BeoPlayer. Click on N. Music, then click on Setup and then click on Scan. BeoPlayer will then do a full search of your computer for music files and will list them on the bar to the left hand side of your screen. These music files will be listed there whenever you next open BeoPlayer unless the music files are moved manually by yourself.
My last check would be that your music is not an MP4 file. My BeoPlayer cannot find MP4 files, nor can the BeoSound 2 play them.
Let me know if you need more help.