Recording quality

Hi at all,
I want to record music with Audacity but i have some quality problem.
My music is mp3 that i play with Windows media player and then I record with audacity setting option Mixage Stereo.
Then When I play i listen low quality, without stereo effects.
But if i record on my notebook i listen record with high quality, why ?
What i must setting ?

Why do that?
You can import MP3 files:

That file is format mp3 but that is a radio stream file