why not have a try the versatile and powerful Aiseesoft Audio Converter?
it can convert among all popular audio formats including AAC, AC3, AIFF, AU, FLAC, MP3, M4A, OGG, WAV, WMA, etc and also it can extract audio from video files including MPEG, MOV, MP4, M4V, RM, WMV, ASF, MKV, TS, MPV, AVI, 3GP, FLV, etc.
just have a try first:
http://www.google.com/webhp?hl=en#sclient=psy&hl=en&site=webhp&q=Aiseesoft+Audio+Converter&aq=f&aqi=&aql=&oq=&pbx=1&fp=ab84f93ce551908a
hope my advice can really help you.