Chorus, It all depends on the room and the speakers. Carpet will absorb frequencies from about three hundred Hz up. Carpet will cut reflections of these frequencies. It will do nothing for deep bass. For point source speakers carpet or a large area rug are a good idea. For linear arrays it makes no difference. For subwoofers it makes no difference.
Frankly, I would ignore the sound and do whatever you find aesthetically pleasing then deal with the sound afterwards which you will have to do anyway. Windows always resonate so I would certainly put drapes in front of the windows. I use digital room control and measure my speakers. The Right hand speaker is next to a window and it's upper mid range was considerably different because of the darn window. I put drapes up and there was still a difference but considerably less.
Frankly, I would ignore the sound and do whatever you find aesthetically pleasing then deal with the sound afterwards which you will have to do anyway. Windows always resonate so I would certainly put drapes in front of the windows. I use digital room control and measure my speakers. The Right hand speaker is next to a window and it's upper mid range was considerably different because of the darn window. I put drapes up and there was still a difference but considerably less.