Personally, I would remove the harddrive, hand your brother the laptop and say "You owe me a replacement."
If I threw up on anything owned by someone else, I'd do whatever I had to to replace it. That's just inexcusable.....if he drove over it with the family car because he sneezed, he'd owe you a new one, right? i mean, I know it was probably an accident, but that's exactly why they call them accidents. When they happen with cars or planes or food, the person at fault pays to fix the body damage, gives you tickets for future flights, or vouchers for free food. Your brother owes you a new laptop, and the old laptop becomes his.
(this is why I hae dorm insurance. Covers all of my stuff in my possession and out of my possession, and other peoples stuff when I'm using it. So if I puked on your computer, I'd send the insurance company $25 and they'd send me a check to buy you a new computer with.)