It topped many Christmas present lists but now the iPod - and its associated online music store iTunes - is the subject of legal action after a consumer decided to take Apple to court because he could not buy the songs he wanted.
Apple, which has transformed itself from struggling computer manufacturer to purveyor of hi-tech cool on the back of the iPod and iTunes, stands accused of anti-competitive behaviour.
The lawsuit, filed by Californian Thomas Slattery, seeks unspecified damages against the company for making iTunes' 1 million-plus tracks only available to iPod users.
Mr Slattery claims he was "forced" to buy an iPod in order to take his music collection, which is first downloaded onto a computer, with him in a portable format. This, he claims, is a breach of US anti-trust laws.
ITunes launched in 2003 and has become the most popular online music store with 87% of the market, according to market research agency NOP World
"Apple has unlawfully bundled, tied, and/or leveraged its monopoly in the market for the sale of legal online digital music recordings to thwart competition in the separate market for portable hard drive digital music players, and vice-versa," the lawsuit said.
"Apple has turned an open and interactive standard into an artifice that prevents consumers from using the portable hard-drive digital music player of their choice."
Apple has sold more than 6 million iPods since it introduced the portable media player in 2001, but that figure is expected to leap to more than 10 million once worldwide Christmas sales have been counted.
An Apple spokesman declined to comment on the case but legal experts said the lawsuit had a minimal chance of success.
"In trying to prove that Apple abused its dominant position in one market - or leveraged that to control another - Slattery will have to prove there was no substitute service and clearly that's not the case," said Mark Owen, a partner at media and entertainment solicitors Harbottle & Lewis.
Since launching iTunes in 2003, Apple has fought calls to licence its music player software to third parties. Last year it acted to prevent rival Real Networks developing technology that would allow iTunes tracks to play on other players.
ITunes uses the AAC format, which Apple says helps guard against music piracy, while rival services such as Napster use a version of Microsoft's Windows Media.
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