I got this from some Brand Name cookbook a long time ago.
1 8-oz package of cream cheese, cubed
3/4 cup Parmesan cheese
1/2 cup butter/margarine
1/2 cup milk (I use heavy cream when I have it)
8 ounces fettucini, cooked and drained.
In a large sauce pan, combine cream cheese, parmesan cheese, margarine and milk; stir over low heat until smooth. Add fettucini and toss.