Itunes issue. i'm trying to listen to music i've purchased on itunes, but it appears to have

Question

i'm trying to listen to music i've purchased on itunes, but it appears to have downloaded as a protected ACC file (whatever that is) and cannot be converted to an mp3 file... any thoughts? i've only purchased a few songs on itunes and obviously don't want to purchase any more if I can play them on my ibulldog.thanks for any help!