converting audio files to mp3 files????????

I am needing a good software to convert audio file to mp3 files. What is a good software to get and easy to use?

 

What type of audio files? What is the file extension?

 

I also need some software like this. I want to convert wav files to mp3 format so that they will play on an average mp3 player..any help?

 

Try this.After the trial period ends the program still works,but without some features.... http://nch.com.au/switch/