By Richard Scott Personal finance reporter, BBC News

Second-hand MP3 players could cost more than you think

MP3 players, such as iPods, have enjoyed huge success in recent years.

The ability to condense an entire record collection into a player you can hold in the palm of your hand has proved a big attraction.

But as they become more widespread, the inevitable second-hand market grows too - and that could cause a problem.

A trawl of online auction sites reveals thousands of players for sale. Many are second-hand, and many come still loaded with the current owner's music collection.

Lawbreaking

And that is where the trouble starts.

The record industry is warning people selling their MP3 players that they could be unwittingly breaking the law by leaving their music on the player.

Some listings on the auction websites actually advertise the fact that the player comes with hundreds, or even thousands, of songs.

The industry says this could mean that members of the public are - intentionally or otherwise - entering the world of commercial music piracy.

Different rules

The difficulty lies with the music's copyright.

In online auctions, preloaded music is sometimes a selling point

It is perfectly legal to sell on a CD with which you've become bored and which you just do not want any more,

But doing the same with downloaded music is against the law - even if you've bought it legitimately.

The law in the UK and the US gives greater protection to the music rights owner in the case of a music download than in the case of CDs or old vinyl.

Online auction sites, such as eBay, say they know about the problem and want people or companies to tell them about auctions that break the law.

But the record industry wants more to be done to educate people before there's a problem.

People today might be innocently selling their players full of music without getting prosecuted.

But over time that could change, as the players become more popular and the issue becomes more serious.

The advice for now is to play it safe - and delete the music first.