Based on personal experience I think it’s tough to make money unless you resell them with a Windows OEM license, or possibly Chrome Flex. That being said, and depending on your area, there’s probably a bunch of businesses, schools, etc that would be happy to let you take old equipment for free. Best of luck to you.
Unfortunately there’s nothing you can do to stop the horns. I did learn from this documentary called Hellboy that you can control them with regular grinding.