How to improve the quality of AMR audio recordings in Windows?
What are you recording? I guess you are talking about the material you were referring to in your previous questions. If so, then you can't really improve the quality.
To be more general: You can't improve the objective quality of a recording after it is done.
You could improve:
If you have a small voice recorder, as I would guess from your questions, you obviously can't change anything of this except for using a directional external microphone which would help make voices stand out from ambient noise.
In my previous answers however I mentioned equalizing as a proper technique to filter noise out and improve voice recognition. This might help you subjectively improve the quality.