Interesting problem ... I tried again to convert an aa file after I have listened to it, and still was able to open it with Goldwave and convert it sucessfully to the mp3 format. I'm not familiar with exactly what encryption method aa files use, but I didn't think there was a flag set after it was listened to ... but who knows. Good luck! I average about 20 hours of mp3 converted aa files on a single 650MB CD ... they sound great.