See if you can duplicate the noise by bouncing the car while it is parked. If you can talk somebody into helping you with this, then you can hunt for the cause. In early models, the stabilizer bar bushings would make a squeaking noise when going over speed bumps that sounded kind of like a spooky door creak. I thought the material used in manufacturing the bushing had been changed by 2000, but it's still where I would start.