Nero has a program included called WaveEditor. Simply drag and drop an audio file and save as .mp3, .wav, .ac3, .aiff, .wma, .mp4, .mwf.
I also have pyro but I had problems activating mp3 encoder on my 64bit system.
I think Nero wave editor has more tools than pyro and for the same price(upgrade) you get all the extra goodies within nero.
What version of nero do you have? I have version 8 which includes Nero WaveEditor. Go to all programs/Nero and look for the sub folder Nero WaveEditor.
Hope this helps.