I downloaded the trial version of Switch 1.13 and successfully converted an mp4 interview to mp3. However, the interview was 90 minutes long, so the trial version only converted the first five minutes. I therefore purchased the full version so I could convert the entire file. However, every time I do this I get the message "one or more files was not converted because it is already in the list". The list is empty. How do I get it to forget that it's partly transcoded it before (if I make copies of the file and change the name, it still recognizes it)?