Well, taking advantage of the great opportunity to replace (not convert!!!!) my 192k vbr mp3 to 128k aac (same quality to my ears for the kind of music I consider) I had re-ripped already about 70 thirty tracks CD's (that is reissue material) when a nasty crash occurred. When I relaunched iTunes all the library info remaining was about the remaining mp3 tunes!!!!! ALL info concerning aac tunes had disappeared!!!! That means I had to return to my last back up. Of course - stupid me - since the iTunes 4 issue I hadn't made any backup. So I had to restart iTunes with a library info containing ONLY mp3 info! That means for me I have about 2000 tracks to edit one by one. (I didn't find any other way and don't think there is...) Poor me! And stupid not making any backup after each re-ripping session. DON'T DO THE SAME! Oh yes: you need to know what caused the crash of course. I was in fact modifying an entry in the info panel when the crash happened. This is maybe the cause. I had to edit the info because some mp3 files where not replaced. This happens when the basic 3 CD infos (Song Name; Artist; Album) has been modified in the mp3 files. This is THE ONLY INFO iTunes takes into consideration when replacing a mp3 file with a aac file (in that case) when you re-rip CDs. The file name (happily enough) is not taken into consideration. mc