Music will not play from mp3 (by 3 users)

I bought a slicK 1GB mp3 player from the family dollar for my niece and she lost the guide to it. I tried downloading music for her but it wont play it, it shows "no file" on the display of the mp3. When I check it in the computer it shows that the music is in the mp3. . .Can you help me in getting the music to play? Thanks.

I also have the Slick Stick MP3 player and it wont play songs. I have syched it about 6 times and when you turn on the player it says NO FILE. I found somewhere it is because of a MICIN.DIR file. But I delete it and it comes right back. None of the songs are protected either.