Another Card Game

[Galilee]

This has nothing to do with the internet or poker, let alone internet poker. But the other Card Game post seemed to go down alright, so here's another one!

Given:

All four aces out of a deck
One new car*
An impartial dealer
You

Problem:

The four aces are placed face down by the dealer - only he knows which card is which. You get to pick one - if you pick the Ace of Spades you get the car. But before the card you picked is flipped over, the dealer turns over two of the other three cards, revealing two aces naturally... but not the ace of spades! The dealer then gives you a choice: turn over the card you first picked, or change your mind and go for the final unseen card ... what do you do?


*a brand new Mini Cooper