How to change a Windows Media music file to an MP3 file?
One of the best tools for converting a Windows Media file — wma, .wmv, .asf, etc. — to the .mp3 format is WinFF. It's a free, multiplatform tool available from the WinFF site. The program can handle a range of conversions and is supported by an online discussion board, a wiki, and more.
Well-known tech author Jake Ludington has a how-to page for WinFF on his MediaBlab site. Jake even provides a video clip showing how to use WinFF. The info is good, but the page is somewhat cluttered with ads for other audio tools, most of which have nothing to do with WinFF, so read (and click) carefully.
By starting with a free tool that I know is a good one, you can gain experience with audio conversions safely and without paying a fee — or taking a shot in the dark with unknown software.
WinFF may turn out to be all you need. If not, at least you'll have a rock-solid basis for comparison when you look at alternative tools. Happy converting!