Preheat the oven to 350 degrees F.
Brown the meat in skillet and drain off the fat.
Return the beef to the skillet and stir in the tomatoes, water and seasoning mix.
Cook for 10 minutes, stirring occasionally.
Stir in ¼ cup of the sour cream.
Place half the chips in a 13 x 9 inch baking dish.
Cover with layers of ½ each of the beef mixture and both kinds of cheese.
Repeat the layers and cook for 20 minutes or until piping hot.
Add the green onions and remaining ½ cup of sour cream on top just before serving.