If you would like to convert audible .aa files to a format that you can play on other devices follow the instructions below. There a a few different ways to do it but this has been the most successful for me. I use NERO 7, Daemon Tools.
-Download Audible .aa files and locate the directory
-Open Nero Burning Rom 7
-Scroll down on the left to "Audiobook CD" and highlight it
-Drag one of the Audible .aa files over to the Nero window
-Save it to the folder or directory you want.
-Click "Autocreate File Names".....nrg files will be extracted from the .aa files to this folder
-Open up the folder these were extracted to and
-Right click on ONE .nrg file and using a virtual cd program like Daemon Tools mount it to a virtual drive
-After it is mounted an autoplay box opens up giving you the option to "Convert Audio CDs to Audio File - using Nero" Click on it.
If an Autoplay prompt doesn't come up, right click on the virtual drive and choose "Open Autoplay..." and choose "Convert Audio CDs to Audio File - using Nero"
When the box opens up you will see the audio files and then click "Copy"
.mp3 files will be extracted from the .nrg files into their separate folders.
Organize these folders by the number of CDs that are extracted. cd1, cd2 etc.