How do you download songs to an xbox 360 hard drive?

I've struggled with this also. I think, that the only way to do it is to put in an audio cd, click "play audio cd" and then "rip cd." That copies the song's to your hard drive. Alternately, you can plug in an ipod or another mp3 player, and the xbox 360 will access the songs on it letting you play them but unfortunately it doesn't let you copy them. Or you can plug in a Window's based pc, and the Xbox 360 will access the songs from your computer.

Refer o your user manual or the Xbox website for more information.
Hope this helps.

How does a cd produce sound ? It's Plastic.?

The surface is covered in a reflective coating, usually aluminum but sometimes silver or gold.

Parts of the surface reflect light well, others don't reflect it so well. The different regions (reflective versus non-reflective) are microscopic in size.

As the CD spins, these regions pass in front of a laser which reflects or not off the surface, and the light when it is reflected is picked up by a photocell which converts it to logic pulses.

These logic pulses represent numbers, which in turn represent a digitized form of the music, very much like a .WAV file on your computer. If you have ever used .WAV file editting software like Cool Edit or Goldwave, you probably have a pretty good idea of how different numbers can be strung together to form a sound on the computer -- a CD player is doing exactly the same thing. It is basically reading a great big .WAV file off the surface of the disk (just like your computer reads one from the hard drive) and plays it out.

The website linked by Mr-Know-It-All just above me is a very good explanation -- the part I think you will be most interested is this sub-page of it:
http://electronics.howstuffworks.com/cd5...

Here is a good picture showing how the "pits" (non-reflective parts of the disc) look:
http://referate.mezdata.de/sj2003/cd_tho...

When a laser spot shines on the surface, the spot is about twice as wide as the track of pits. If the spot is shining on a flat part of the surface, it is all reflected back and the photo-sensor "sees" the light. But if the spot is shining on one of the pits, some of the light is in the pit and some is not. The pit is a very precise depth (exactly one quarter of the wavelength of the light used, or about nine one-millionths of an inch deep) and due to a funny property of laser light, the part of the light reflected from the "surface" is canceled out by the part of the light reflected from the "pit" so the photo-sensor does not see any light. The website shows this as light being deflected away from the sensor by the "bumps" -- this is not exactly how it happens (it is based on the "destructive interference" of laser light which I just descibed) but it is close enough and probably a lot easier to understand.

Here is more information on how the discs themselves are manufactured:
http://www.ee.washington.edu/conselec/CE...