I'm sorry that you've been jumped on for asking a perfectly legitimate question. There are plenty of free legal tracks on the internet as Sethhaniel and Salinger have pointed out.
Special software is not required and windows own media player is fine for most downloads. There are one or two other free players that can be downloaded to your machine as well to allow you to copy/save free music.
Try this site for several links to either copyright free music or tracks that are copyright and you pay a small fee to download from. click here
Napster. Now legal and you pay for the music but at least you can choose your own tracks and end up with a CD full of music you want rather than paying for 15 tracks of which you only want 1 or 2. click hereclick hereclick here are a few sites to get you started.