Crush the pretzels by placing them in a Zip-loc bag and rolling over them with a rolling pin. Alternatively you can use a food processor.
Mix together pretzels, melted 3/4 cup butter, and 4 T sugar in a small bowl. Pat into a 9x12 baking dish, and bake at 400 degrees for 6 minutes.
Cream together softened cream cheese and 1 cup sugar. Fold in entire package of Cool Whip. Spread over cooled pretzel layer.
Prepare Jell-O with 2 cups boiling water, stirring until completely dissolved. Add still-frozen strawberries.
Wait until the Jell-O is just starting to gel, then pour over cream cheese layer.
Chill 1 hour or longer to completely set the Jell-o.