ya all home stereo systems bought as a package come with some sort of reciever, amplifier. it is the thingy that you turn the volume up and donw on, and change the radio station. If that hepls any.
Now on the back of the receiver there are some red and white plugs that say adio inpput or something along those lines. You just plug a "y connector" ( has a red and white plug on one end and a hedphone jack on the other) into the back of the receiver( the red and white side) then youi plug the headphone end into the sound jack in the back of the computer.
the viola you have instant DIY DJ