Ok, if the player states that it is a unknown format, it means that the songs which you coppied to the device is not in mp3 format.
Here is how you change it to the right format:
Go to the link and download the free mp3 converter software.http://www.wma-mp3.com/
All To MP3 Converter 2.1This should help you. Leave a comment if you can't figure it out.