A friend suggested this recipe. It came from the Kraft recipe book which you can subscribe too. They send them out at no charge 5 times a year. They always have some really simple and great recipes in it. You can see them here, and find where to sign up to recieve them as well.
1 box mac and cheese
1 lbs ground beef
1pkg taco seasoning
3/4 cup water
3/4 cup sour cream
1 1/2 cups shredded cheddar cheese
prepare mac and cheese as on box then add sour cream. brown ground beef, drain and add taco seasoning simmer 5 mins.
put 1/2 mac and cheese into pan then all of the ground beef and 1of cheese and then the other 1/2 mac and cheese. bake @ 400 for 15 mins then top with salsa and rest of cheese. bake 5 mins more.