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In a story that sounds like the start of a Hollywood blockbuster, a New Zealand man got the surprise of a lifetime when he plugged in his MP3 player and found confidential United States military files.

Chris Ogle, 29, from Whangarei, bought the player from an Oklahoma thrift shop for $18, and found the files when he hooked it up to his computer, One News reported tonight.

The 60 files on the player contained the names and personal details of American soldiers, including ones who served in Afghanistan and Iraq.

There was also information about equipment deployed to bases and a mission briefing.

"The more I look at it, the more I see and the less I think I should be," Mr Ogle said.

Victoria University strategic studies director Peter Cozens said one of the first rules of military endeavour was to not give the opposition information that could compromise your position.

"This is just slack administrative procedures which are indeed a cause of embarrassment. It's the sort of thing which ought not really be in the public domain", he said.

Mr Ogle said the player never worked as a music player and he would hand it over to the US Defence Department if asked.