... And put what on it? ...
There are only two "consumer ready" Operating Systems currently on the market - Windows, and OS X. And I think it is pretty clear that Apple has no desire to allow their OS to be installed on all x86 64 hardware.
Oh and please don't give me junk about Ubuntu ... Those guys are so busy making sure their 3D cube windows can spin in every which direction, they forgot to address usability.
Couldn't agree more on Ubuntu.
On the matter of bundling, I'm guessing separation wouldn't have much effect - people would still buy Windows. However it is a pro-competition move that just might impact pricing when people start making conscious decisions about what to get installed. Worse
things could happen, from my perspective.