Is this the foot you're trying to use?
http://www.amazon.com/Janome-Embroid.../dp/B0042ICC7K
If so don't use that in your 6600...that's only for embroidery machines, not the sewing machine! It's the foot that my Janome 350e uses...I just went to look and sure enough there is the P stamped right above the open space in the foot! Not the one you want!
Did you buy your machine used? It's possible someone mixed up the feet. If you bought it new from a dealer it should have the P2 foot in the box with all the other presser feet too.
Edit: DogHouseMom your pictures are MUCH better than mine! My camera is old and my photography-fu is not so strong :mrgreen: