I would be wary of using software such as Limewire,as it's peer 2 peer,and although you will get the mp3 you want,you dont know what other code comes with it.Yet there are legal sites on the web that give you freebies,as the idea is to keep you legal.What you do is up to you of course,but illegal downloads are not encouraged.
As suggested,look up free mp3 in a search engine,as you should get a lot of sites,but stay clear of file sharing as spending Sunday cleaning up your PC will be no fun at all.
