Combine the first 6 ingredients in a saucepan; beat at high speed of a mixer 5 minutes. Add vinegar; beat at high speed until blended. Bring to a boil over medium heat; cook 1 minute, stirring constantly. Remove from heat. Add margarine, and beat at high speed 1 minute. Cool. Combine spinach and next 3 ingredients in a bowl, and toss gently. Pour dressing over spinach mixture; toss well. Top with croutons.
Calories 75 (30% from fat); protein 3.4g; fat 2.5g; carbohydrate 10.1g; cholesterol 27mg; sodium 260mg.
