Why does Window Media Player keep deleting everything on my mp3 player EVERY F*CKING TIME I sync anything?

I'm trying to fix some of the names on my mp3 player, so I figure, why not use Windows Media Player? But, every time I sync even ONE song, wmp deletes EVERYTHING on it. WTF! It's pissing me off. PLEASE TELL ME HOW TO MAKE IT STOP!!!!!!!