This is a great way to use up leftover spaghetti.
In a large pot bring water to a boil. Add the spagetti and cook until al dente. Drain and set aside.
Preheat oven to 300. In a large saute pan over medium heat, saute the chopped onion until translucent. Add the soup, water, and cheese. Heat this mixure, stirring constantly, until the cheese melts, then remove pan off the heat. Add the ham, spaghetti, and peas, and mix well.
Pour mixure into a 9x12 baking dish, and cover. Bake 10 to 30 minutes.