To explain the nature of Iron Man's origin story, we must first explain the concept of a sliding timeline.
A sliding timeline is a form a retroactive continuity that is used to explain why characters have not aged over significant periods of time. This is done by taking a soft stance when it comes to the date of previous events - although a certain Spider-Man story may have been released decades ago, the characters might refer to it as if it happened fairly recently. This results in a world where an impossible number of events can happen in a very limited amount of time, ensuring that although writers come and go and major real world events happen (and are often alluded to), the characters never have to age.
This causes a problem when a character has an origin story based around a real world event. The comic that you are reading is usually set in the modern day, but the character you are reading about is still the same age as he was when the Vietnam War happened. To get around this, a "retcon" is used to alter the characters past and bring it closer to the current date to avoid a major disconnect between time elapsed and the character age.
This is why the 2005-2006 comic arc Extremis, Tony Stark had his origin story altered to have taken place during the Afghanistan war, rather than the original setting of the Vietnam War. The events as they happen are mostly the same, it's just the time and the location has been updated in order to retroactively fix an impossible element in his continuity.
It is this origin story that the 2008 Marvel Studios film Iron Man uses, and as far as I am aware is the origin story currently used by comics set in the Earth-616 continuity.