They're not MP3s, they will be unprotected AACs, so actually they will play on any player that supports AAC. But you can easily make an mp3 copy within iTunes by right clicking on the song and selecting "create mp3 version."
I live in England and I have just found out from the BBC news that iTunes music downloaded from today can now be played on ANY MP3 Player! Hurrah the monopolisation of the music industry has ended.

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