It's best to save any music directly into mp3, not wma. These are compressed formats & each time you convert there will be quality lossed. wma = audio format, wmv = video format. mp3 = audio format. If your file is lossless wma format then it's safe to convert it to mp3. wma lossless will = about 1 min per 6 to 10 MB I think but not sure.

I guess it depends what your situation is. If you are downlding wmv files & wanting to convert to mp3 (& whether this is for others to share or so you can play them), or whether you are extracting music from a cd, converting to wmv & then wanting to convert to mp3.

One suggestion is QCD: http://www.quinnware.com/
Xtra plug-ins here: http://www.quinnware.com/plugins.php It will play or convert wma files to any other mp3 or ogg vorbis formats.