Excuse if I chime in...
wma is audio thats correct, it stands for win media audio
wmv is win media video
MPEG, the moving pictures experts group, has lotsa standards. one of them is MPEG 1 layer 3, commonly known as mp3 ; as we all know thats just audio, no video. mp3 works with filters to reduce the data volume..
then there is MPEG 2, for example AAC, the advanced audio thingie, which is dolby 5.1/ surround sound compatible.
and then you got certain video formats by MPEG. MPEG 4 is for audiovisual data. Now this has lotsa possibilities, from integrating synthetic sounds to the complete digital reconstruction of pictures etc. etc. MPEG developers wanted this standard to be as safe as possible, also in mobile computing, handy, PDAs etc.
Now there is MPEG 7 and MPEG 21. reminds me of when I studied psychoacoustics
- but those two formats are surely not the ones that tarvark meant.
I think tarvark probably meant how to convert a wma file to an mp3 file (mpeg 1 layer 3)
do a google search for wma mp3 converter, there are lotsa free sites that offer those little programs. I either convert in nero burning rom or in other, bigger programs, sequencer programs, wavelab, etc.