I recently got a Sansa Shaker and I can not download most of the songs I want on to it. I have only down loaded songs that say mp3 but when they are put on the memory card it says it is a wma file and it won't play. Also my computer says it is converting them but I guess it is not. Can anybody PLEASE tell me how to tell if a file is a true mp3 file. I am so tired of downloading songs I can't use.