Get a free music converter, google it
Decode the WMA to WAV. I'm not sure how you do this in windows, you can find out with google. Then encode that WAV to MP3 with the LAME encoder, just google that, too.
go download a mp3 converter. theres lots of free ones for download online. the one i got is called Switch.
file converter i imagine?
u can use itunes as it converts it then adds to your itunes library. be careful though. the default is set to convert to AAC (another annoyin music file like WMA). you have to go to preferences to change it to MP3. its one of the quickest and easiest WMA to MP3 conversions i know and its the only one i use. hope this helped