Preheat oven to 325. Prepare a 10" spring form pan with cooking spray; set aside. In a mixing bowl, combine crushed cookies and margarine. Mix until crumbly. Press mixture firmly into prepared pan; set aside. In another mixing bowl, combine cream cheese, sugar, and vanilla extract until smooth and well blended. Fold in melted chocolate and eggs. Mix well. Pour over crust. Bake for one hour, or until center is almost set. Run a spatula around rim of pan to loosen cheesecake. Cool before removing rim of pan. Refrigerate for four hours or overnight.