1. Bring a pot of lightly salted water to a rolling boil; cook the macaroni in boiling water until cooked through yet firm to the bite, about 8 minutes. Drain. Chill in refrigerator.
2. Bring a separate pot of lightly salted water to a rolling boil; cook the potatoes in boiling water until just cooked through, 20 to 25 minutes. Drain, peel, and chop the potatoes into small cubes. Combine the potatoes, chopped egg, and mayonnaise in a bowl; mix. Add the macaroni, Italian-style salad dressing, onion, carrot, salt, and pepper to the potato mixture; stir. Chill in refrigerator until cold, about 20 minutes. Serve cold.