Thanks for the replies, but isn't Pr(A and B) = Pr(B) if A is the event 'exactly one ace'? Here, it is at least one ace, so there can be 1 - 4 aces, but the ace of spades always has to be in the hand. Thus, the possible combinations can be:
Ace of Spades x another 4 cards
Ace of Spades x Ace...