In a medium saucepan, cook spaghetti according to package directions. Meanwhile, slice cheese bar into small cubes.
Drain pasta and return to saucepan. Add Italian diced tomatoes and cheese cubes. Cook over medium heat, stirring frequently, until cheese is melted and dish is heated through. Salt and pepper to taste.
Serve with a garden salad, your favorite Kraft dressing, and garlic breadsticks.