How do I get hard water stains off my car window and windshield?

I have had a sprinkler system and hot sun hit my car for weeks. I, through research and a lot of elbow grease, have managed to get the calcium stains off my black paint, but am having problems getting the circular hard water stains off of my windows and windshield. I have tried vinger based products, CLR, newspaper buffing, and other methods. I am wary about using a #0000 pad because I am afraid that I might scratch the gl. Any thoughts and suggestions would be welcome.