Ok, maybe I was a little short. Let's say that you buy a new stereo system. You take a picture of it installed, and put the picture, along with the papers and receipts, into a carton in your garage. New hub caps, same way. If the car was stolen or damaged, you'd have proof of what you had in...
I've never had a car, so you know what this advise is worth. I'd get myself a camera and a box. Whenever something was done to my car, I'd put the papers into the box and take a picture of it. Any insurance company would have a hard time arguing with that! Glenn