But to get back on topic, dBpowerAMP is very good at audio file format conversion:-

A free version can still be found at- http://www.pricelesswarehome.org/200...IA.php#0898-PW

Extra codecs (over and above those included by default) can be obtained from Codec Central- http://www.dbpoweramp.com/codec-central.htm

But, as stated above, wma to mp3 is a bad idea.