There is a way to use iTunes to convert to Advanced Audio Coding (AAC) in iTunes. There are several music players which only use this format or that work better using this format instead of MP3 or WAV. The new upcoming Nintendo DSi is coming out soon and many are scrambling to find a way to convert their music files to AAC for playback on the new portable system. It is easy to convert music formats in iTunes, but not quite obvious how to do so.
Open iTunes. Go to Preferences, and under the General pane choose Import Settings.
From here you can choose which format you want for conversion. You can choose Apple Lossless Encoder, AIFF, MP3, WAV, or in this case we are choosing AAC. Specify the quality you want for the file. Click OK.
Now select one or more of the files you want in the main Library window.
Go to the Advanced menu, and choose Create AAC Version. Now it will quickly convert the file or set of files for you.