Back in 1999, Shawn Fanning, then a 19-year-old student, could never have predicted the extent to which his simple computer program would change the music industry forever.

Napster’s peer-to-peer file sharing system was perhaps the most highly publicised of its time and it was not always good publicity.

The Recording Industry Association of America (RIAA) was less than impressed at how easy Napster made it for people to download music free of charge. They were quoted in the media at the time calling Napster "an instrument of shoplifting".

The RIAA proceeded to sue Napster saying "Napster knowingly and wilfully set out to build a business based on copyright infringement on an unprecedented scale."

Shawn Fanning says his original intention was never to make money from the site. He claims he had only been trying to make it easier for his friends to share digital music files.

A few years later, the lawsuit was dropped but a new ruling meant Napster was effectively unable to continue legally operating under their existing business model.

One thing Napster had proved was the enormous global appetite for sharing and downloading music. And where there is a healthy demand, there is usually a healthy profit to be made too.

So, unsurprisingly, the music industry followed suit and the big record labels now play a key role in hugely successful ventures such as Apple iTunes, Yahoo Music and Spotify. Napster has also relaunched itself with a more viable and legal business model in which people pay a small fee for downloading songs.

Turning your home PC into a modern-day jukebox has never been so easy. But with illegal file sharing still easily accessible, it is yet to be seen how viable in the long term these new legal music sharing sites are.