Just a shot in the dark, but what app are you playing the MP3 through? I'm assuming it's Winamp based on the original post. Does Winamp have a built in equalizer or tone controls? If so, how are they set?
How are the tone controls set in Windows? They're buried a few layers deep in the audio control panel. Getting to them takes hitting two "Advanced" buttons.
How are the tone controls set in Windows? They're buried a few layers deep in the audio control panel. Getting to them takes hitting two "Advanced" buttons.