This is not an uncommon problem! Verify the following: 1) Verify that your new music files are in the correct directory where you know at least one MP3 (demo?) file is working. 2) If the music files are correctly located on your MP3 'drive', check that you are using the correct naming convention (file name not too long and with .MP3 or .WMA in general) by comparing it with a working file. As a rule, files from an audio CD or .WAV files will not work on MP3 players. 3) Your new songs that can play on your PC may be compressed/encoded in a format not compatible with your (relatively cheap) player: look at the 'properties' of a working songs on your player and compare it with the one that do not work: the issue is usually the 'bit rates' (128mbps fix rate is usually a good one to use). Hope it helps! ps. There are many free audio media format converters that you can download.