I downloaded the free version to see if I liked itm and if it actually worker. so far, I can't get it to work. I wanted to open an mp3 file to edit, and it keeps aying the file is empty. If this needs to be activated, since I got the free version, there is no serial number, so I don't know what I am supposed to do. Extremely frustrating.
It appears that working with mp3 files is an optional add-on for the Free edition (see notes below grid). As a temporary workaround, you could open the mp3 file in something like Audacity, and export it to wav format.