Jin1976, you may want to try and locate something called rouge. It's a very fine polishing powder, used in the jeweler industry. I've heard reports that buffing with rouge can remove scratches from glass if they're not deep... I know there are different grades and fineness to them, but I don't know the details. At any rate, it's worth a try if you can find it, CERTAINLY cheaper than a windshield replacement!
Remember, too, that if you have a choice between more abrasive and less abrasive, to start with the finer grade and work up until you get results.
Good luck!
Don