New to N7

[KDery]

I just purchased my N7 2 days ago, transferred some music yesterday, went to find some CD's that were not already on my computer. I ripped them into windows media player, tried to transfer them to N7, it appeared that they transferred, spent like an hour doing this only to find that they did not transfer. The first batch transferred fine, the second ones did not. I even made sure that they were mp3's and they still did not transfer, any suggestions?