[Air-l] Downloading music

Hi Can anyone clarify for me when it's legal/illegal to download music from the internet. I've just checked out sites like http://www.mp3musichq.com/me/index.asp?source=guks-03&kw=limewire which say that it's legal as long as you follow the copyright rules. I have also read articles saying that some companies are releasing stuff by up and coming bands for promotional reasons, that is free to download online. But, the stuff on sites like limewire is more far reaching than just new/promotional. I had assumed that if you didn't pay for it it was illegal. But having interviewed many 14 year olds about it this week, this is clearly not their understanding. Thanks for your help. Sue