I think the reason Apple automatically converts music files ot AAC is because AIFF and Apple Lossless Encoder files won't play on iPod shuffles.
If you wanna convert them back to lossless, this article might help:
Thanks Velskud. The article is perfect. But is AAC a more compressed audio file than Apple Lossless? If so, can I really get the fidelity of the Apple Lossles audio file from an AAC file. From the article:
"Once a song is compressed (meaning some of its data is lost) you cannot retrieve the data by uncompressing it. If you convert a song from a "lossy" format to a uncompressed format, the quality of the song will not improve and the file will only take up more disk space. For example, if you convert a song in MP3 format (a compressed format) to AIFF (an uncompressed format) the song will take up much more space on the hard disk, but it will still sound the same as the compressed file. In order to take advantage of uncompressed formats you should only import songs using these formats.:
Is AAC a compressed format? If so, maybe I need to ask Western Digital why they converted my Apple Lossless audio files into AAC.