Convert+iTunes+to+MP3

=Saving a copy of a song in a new file format= source: itunes HELP

You can convert a song to a different file format while keeping a copy of the original. For example, you can save a copy of a compressed song file such as MP3 or AAC in an uncompressed song format (AIFF or WAV). When converting from a compressed to uncompressed file format (for example, from MP3 to AIFF), you shouldn't notice any reduction in sound quality. However, when converting between compressed formats (for example, MP3 and AAC), you may notice a reduction in the sound quality. For the best results, if you want your music encoded in a different file format, import the music again from the original source using the new encoding format. Important: Except for iTunes Plus songs, you can't convert iTunes Store purchases.

To convert a song's file format:
==To convert all the songs in a folder or on a disk, hold down the Shift key and choose Advanced > "Convert Selection to," then choose the folder or disk containing the songs you want to convert. ==
 * 1) Choose Edit > Preferences, click Advanced, and then click Importing.
 * 2) In the Import Using pop-up menu, choose the format you want to convert the song to, and then click OK to save the settings.
 * 3) Select one or more songs in your library, and then choose Advanced > "Convert Selection to...."

The song in its original format and the newly converted song appear in your library.