Preheat oven to 375°F. Crush whole bag of corn chips, set aside. Combine cooked chicken, dry mix, soup, and Velveeta in sauce pan, cook till cheese is melted on low heat, stirring frequently.
Pour 10 oz. can of enchilada sauce in 13x11x2-inch baking dish, spread evenly. Spread 1/3 of the bag of corn chips on sauce. Add sour cream to chicken mixture after cheese has melted, pour over corn chips. Top with remaining bag of chips. Pour 14 oz. can enchilada sauce over all, may have to insert knife in parts of chips so all will pour in.
Bake for 45-50 minutes. Top with shredded cheese; bake 10-15 more minutes. Let stand for 10 minutes before dishing.