If you do a lot of work with audio on your Windows machine, one great tool to consider is the FairStars Audio Converter. It can convert audio between just about any formats. In addition the its breadth of supported formats, a couple of my favorite features are:
- batch conversions - if you have a bunch of files encoded one way and you want to convert them, this is the program for you. Let's say you have 100 WMA (Windows Media Audio) files and you want to convert all of them to MP3. No problem. Just drag and drop them in the FairStars and you're off
- preservation of ID3 tags - FairStars can actually preserve your metadata when doing conversions, which is HUGE. If you have laboriously ID3'd hundreds of MP3's, you don't want to lose that data in the conversion!
The reason I originally came across Fairstars was because I was trying to help someone convert hundreds of problematically encoded files to a usable form (they were stereo files with audio on only one track - you would only hear audio from your left speaker). Since the files were just voice recordings, we decided to collapse them to mono MP3's. FairStars did the job very well and saved us a bunch of time.
Definitely worth a look if you're into audio.