well, I guess there'll be two very big slots( for X Flash, Smart Media etc.). Ofcourse, Duo won't go into that. Out of the two left one is for the Noia MMC Card or MS card. The other is for Duo.
The key point is that you have to insert the duo with the reverse inside i.e. if the card reader is placed with its name on the top, then insert the duo such that the golden conductors are visible to you and the duo is on reverse. Got it? I hope so