I most definitely wouldn't buy a computer with Linux pre-installed. Not even my favorite distro. I want to do it myself.
However, my problem is that I've bought 3 laptops in my life, and with each of those I bought a copy of Windows. The copy was deleted and the stickers peeled off, but Microsoft still got my money for doing nothing. And that's totally unfair.
So I agree, empty computers would be good. Sell empty computers, and Best Buy offers to install Windows for you.