It's not necessarily the windshield itself, rather the frame around it. I am not sure if this is the culprit as I would have to hear the sound in person. It will usually get worse the colder it gets. This should not be happening as this may mean a structural defect in the frame of the car, possibly a missed weld or loose bolt somewhere. Take Drucks advice and take it to another dealer. This seems to be an isolated issue, and do not take "those noises are normal" for an answer. Also, I would call the Ford hotline and report the dealership where you were told that you have to spend $100,000.00 to have a car that makes no unusual noises........Ford will contact this dealer and reprecussions will ensue.