In a large bowl, stir together the gelatin and boiling water until gelatin is dissolved. Chill until partially set.
Stir in strawberries, pineapple, bananas, and walnuts.
Turn half of the mixture into a 3-quart rectangular (13x9x2-inch) dish. Place in your freezer for 10 to 12 minutes or until firm.
Spread with sour cream. Spoon remaining strawberry mixture over sour cream. Cover and chill for at least 4 hours or until firm. Makes 24 side-dish servings.