taipan

Hi all, first i wanna tell you guys that I'm from Holland so my english probably sucks, so sorry for that. I've bought a sony nw-107 and i've tried to put music on it. But everytime i trie to transfer music on my walkman it says that all songs cant be transferred. They are all mp3 files so i have no idea whats the problem. Ive searched for hours but cant find a solution. I really hope one of you guys could help me out! Thanks and greetings, Rene