Place frozen chicken in bottom of crockpot. Sprinkle taco seasoning on top of chicken breasts and dump the cans of tomatoes and green chiles and nacho cheese soup on top of that. Cook on low for 6 hours.
Cut chicken into chunks and spoon into taco or tortilla shells, or place on bed of lettuce for taco salad. Spoon some of the cheesy mixture over chicken and top with favorite Mexican toppings. We serve this with rice and beans, and it's always a hit!