Preheat your oven to 350°.
In a large skillet over medium-high heat, saute the hamburger and cook until almost cooked through.
Add the onion, peppers, garlic salt and pepper ad cook until the veggies are cooked through.
In a medium saucepan boil water for pasta . Add pasta and cook until pasta is just al dente. Do not over cook as the pasta will continue to cook in the oven. Drain.
Add the cream cheese. If you didn't leave it out at room temperature you can microwave it for a minute in the microwave. Add sour cream and Parmesan cheese.
In a sprayed 9"x 13" casserole dish, add the pasta mixture. Then add the hamburger mixture and sauce on top and stir until everything is loosely combined.,
Top with the shredded cheddar or mozzarella.
Bake at 350° for 25-30 minutes, or until the casserole is heated through. Serve immediately.