WinFF is a frontend for FFMPEG. It's a crossplatform, opensource application that can easily convert any audio or video format to any other audio or video format you need.
It can convert xvid to mpeg to avi to mp3 to wav to flv to 3gp and a lot more. Try out any video or audio format you may have, and this baby can convert it for you. It's free and easy to use.
Try it out for XP or Linux. I love this app and I use it to convert my favorite podcasts to 16k MP3's.
You can also try Cdex for free audio encoding and CD ripping.
