Just to say Ubuntu does come preinstalled on some dell computers.
I know and acknowledge that, but it obviously hasn't been as much of a viable commercial alternative as they would want it to be. If it was, then it would have been replicated on a large scale by other major computer manufacturers. I'm not saying that it's never been done - I'm just saying that it's not very practical for a company to devote a large amount of it's computers to a Linux system.