Convert an mp4 video to an mp3 audio from the Advanced menu in iTunes. (It's how I created the ringtone on my phone) But the option is greyed out now. Anyone know what's goin' on?

When I've wanted to convert to mp3, I just burned a CD in iTunes (usually burning to an image, IIRC), and re-reipping the CD to whatever format I wanted.

Convert AAC files to MP3 in iTunes There are various dedicated audio conversion software packages available, but the best one is probably already on your hard drive, as it’s iTunes itself.