I think when they were hung drawn and quartered, they weren't hanged, because the fall is meant to break their neck when their hanged, but when they're 'hung' they don't have such a big fall as they dont' want them to die....<stabs in the dark>
hanged to go from alive to dead, as consensus (ooh, I've used that twice today!)
hung if its state of living hasn't changed. (pictures, like a donkey, meat etc)
hung, drawn and quatered is techincally incorrect, as the hanging part killed them, then their corspes were drawn on and chopped into 4 (down and then across). the hung part came because of ease of saying it, but offically, the judge would have said Hanged, drawn and quartered.
so, if you killed the animal by hanging, then it was hanged, and if you put it on a hook after it was already dead, then it was hung.
"Hanged" is for when a human is executed by use of a noose; "hung" is for everything else (meat, pictures, etc.)
"Hung, drawn and quartered" - I've always understood this to be the use of a noose to strangle but not kill, then the person is "drawn", i.e. his abdomen is cut upon and his entrails are removed while he is still alive, then his body is "quartered" by chopping it up for display in different parts of the city.