Heat oven to 250°F. Cut 2 large sheets of foil. Place popcorn and peanuts in 2 ungreased 15x10x1-inch baking pans.
In medium saucepan, combine butter, sugar, gelatin, water and corn syrup. Cook over medium-low heat until sugar and gelatin are dissolved, stirring constantly. Using candy thermometer, continue cooking to 255°F. (hard-ball stage), stirring constantly. Pour syrup over popcorn and peanuts; stir to coat. (Mixture will be hot).
Bake at 250°F. for 15 minutes. Stir mixture; bake an additional 10 minutes. Remove from oven; immediately turn mixture out of pans onto foil. Cool 30 minutes or until completely cooled. Break into small pieces. Store in tightly covered container.