It's illegal...a few years back is when they got busted and many people who had it had to pay fines well into thousands of dollars. A good website, aside from limewire (sometimes it makes your pc run slow), is bearshare. You can go to: www.bearshare.com and download the free program or there is one that you can pay for and it has more options.
don't go there hun, kazaa or limewire are a no no, they really ruined two computers I had the amount of adware, spyware etc was a joke. Try these free sites that I use
www.blubster.com or www.bearshare.com these both have free versions and are legal