Which Door Hides the Gold?

You face three closed doors, labeled A, B, and C, with the knowledge that a bag of gold lies behind one of the doors, with the others offering nothing. Your host, who is also unaware of where the gold lies, gives you one chance at collecting the gold, provided you select the appropriate door for him to open. You pause for a moment, and then select Door A.

Before opening Door A, however, your host states that he will go behind the doors and open either Door B or Door C, on the condition that he will not open any door that hides a bag of gold. Your host then opens Door B and offers you the opportunity to change your choice to Door C, rather than Door A. You now face two closed doors. Should you accept this offer, or will you remain commited to Door A in your quest for the gold?