Cook spaghetti as directed on package; drain.
Meanwhile, in 10-inch nonstick skillet, cook beef over medium-high heat 5 to 7 minutes, stirring frequently, until thoroughly cooked; drain. Stir in taco seasoning mix and water. Heat to boiling. Reduce heat; simmer uncovered 3 to 4 minutes or until thickened. Stir in pasta sauce; cook over medium heat until hot. Stir in cooked spaghetti.
Meanwhile, heat taco shells as directed on box. Spoon about 1/2 cup spaghetti mixture into each taco shell; top with tomato and Parmesan cheese.