wma files

I was updating my windows media player from version 9 to 10 and I backed up some of my wma format movies and music off of my computer to a cd-rw just incase something went wrong. In the process, I think my lisence (*.bak) files got deleted or something. It cannot play the files that are on the cd-rw. (I moved the files back onto my computer.) I tried running it and it says getting lisence and then later on it says error, couldn't get lisence. Are there any ways to get the files to play? Thanx.