I have an iPhone 3G 16 GB that's running out of room. My iTunes library has gotten larger over the past few months and as of right now I only have 166 MBs left on it's internal memory. The majority of this is taken up my 2300 or so songs. I have noticed that a lot of my iTunes library is in .mp3 format. Now I just finished watching Donald Bell's video on CNET that explains the differences between different audio formats and from what I gathered AAC files are slightly smaller and keep nearly the same audio quality. If this is true, I want to go about converting my entire music collection to AAC format, however I can't find an easy way of doing this. I have looked in the options for Smart Playlists and I don't see any file type filter. Do you know of any way put all the .mp3 files together and convert them to AAC all in one shot, preferably in iTunes itself? Thanks in advance for the help.