Go get VLC PLAYER and see how it sounds there. If it's OK then it's a WMP issue.
I have Audacity 1.2.4 and it does real well converting my analog music into .wav files and finally to mp3 format. When I play back the newly converted mp3s in the Audacity player, they sound fine but when I play them using the Windows Media Player like I do with all my mp3s, the sound is really weird and unacceptable. I know that Audacity features an Effects menu but it is not easy to use. And trying to use the Audacity forums to get information is really screwy.