When the US record industry took on Napster and won, it could have been forgiven for thinking it had strangled the piracy craze at birth. Instead, Napster has been replaced by more sophisticated services.

Napster's key weakness was its reliance on a central computer server system to hold a central index of all files available on the network - an easy target for the industry's expensive lawyers.

But the services that have thrived since Napster's demise are decentralised, allowing users to directly search the computers of others in the network to find the files they want.

To become part of the MusicCity network, for example, users simply download the Morpheus software from the website. To locate an episode of say, The Simpsons, they type the details into the search box. The request automatically goes to the local "supernode", a more powerful computer owned by another member of the network. This in turn searches the hard drives of other users. Within a few seconds, a list of Simpsons episodes available for download appears on the original user's screen. They then select the one they want and download it.