Preheat oven to 350 degrees. Melt Velveeta in heavy pan over low heat, stirring. Add Mayonnaise and potatoes to cheese and mix well. Put into a 9 X 13 inch shallow baking dish and top with bacon. Bake, uncovered for 35-40 min. until bubbly and golden brown. I double this recipe and increase cooking time to 1 hour.