Mix sugar, crushed pretzels and butter in 9 x 13-inch pan. Press tightly; then bake at 300 degrees for 15 minutes. Cool.
Cream together cream cheese and powdered sugar. Fold in whipped cream, then marshmallows. Spread over cooled pretzel crust.
Dissolve Jell-O in hot water; add cold water. Stir in berries and chill until slightly thickened. Pour over whipped cream mixture; chill until ready to serve.