In frying pan, brown ground beef, then add taco seasoning and the suggested amount of water listed on the package. Add can of refried beans and chili powder and cook/stir until well blended. Spread in bottom of 9x13 pan. Spread sour cream over hamburger mixture and cover with shredded cheese. Bake at 400 degrees until bubbly around the edges. Serve hot with tortilla chips.