This is just a thought, with no experience behind it what-so-ever, but... They're selling headlight restoration kits now- I'm not confident they would do the job, but it's way cheaper than a new windshield. I think Valker's suggestion is essentially the same idea, and Novus has got a good reputation. Perhaps buy a Meguiars or Mother's polishing ball, or similar, and give it a whirl (pun intended- did you like it?

). If heavy, aggressive polishing doesn't work (most of these polishes have "diminishing crystals," so they're not going to scratch or make your windshield worse, even if they don't work.), then go for the new windshield.