Tevion mp4 player trouble with downloading?

recently bought a tevion 4gb mp4player from aldi,I have had say 15 songs on it and now want to change them so that I have a fuller more varied library of songs but when trying to sync my mp4 to the library of chosen songs the computer displays a message saying "harddrive or devise has no space to store data" so I have deleted all songs from devise but still unable to sync with mp4 player?Any suggestions?