Musique MP3

Hello, I put music on my MP3 without any problem after downloading it on the computer. But when I decide to put it from a CD, and I start the synchronization, Windows says that it finds an error, that the music must be properly saved on the computer, so in my music folder. But I have saved everything....!!! If someone can help me solve this problem!!!! THANK YOU IN ADVANCE. CHRISS...^^

(PS: my MP3 charges via cable on the computer and uses a micro SD card for music).