amp16751

I recently purchased a Lexar 128 MB SD card. I loaded several MP3 files on the card using Windows Explorer on my PC. I then made a Playlist in Windows Media with all the MP3 files I initially copied onto my SD card. I then copied several more MP3 files using Windows Explorer on my PC. I wanted to add several additional MP3 files to my original Playlist. When I tap on the add icon in Playsist and then tap on the SD card folder I cannot see all of the MP3 files on the SD card. Only some of the new MP3 files are visible in the list. I can however find them on the SD card using Windows Explorer from my PC through Autosync. Any reason why I am not seeing all of the MP3 files using Windows Media Playlist?