Telling the difference between zinc and aluminum

Found this on treasurenet.com... I have some laptop hinges and such that I think might be zinc. If aluminum I plan to melt them down with the 50lbs or so of hard drive cases I've accumulated. Spring fever, time to melt some metal! Anyways, this is what they wrote:

Quote Originally Posted by pepperj
"It's been a few years now, but I recall that if you file the metal and put vinegar on the zinc it'll foam up a bit. On the aluminium the vinegar will stay clear."