I'm sure Steve Ballmer will not complain if you decide to spend $189 for Widows 7 Home Premium (full install, since you have nothing to upgrade

) for your MacBook Pro. He may not encourage it, but he'll gladly take the revenue . . .
I actually think that it's funny that Apple's true competitors (for Macs) are the hardware OEMs that make Windows computers, more than Microsoft. Each MacBook sold is still a potential Windows license, but it will never be a Dell, HP, et. al., sale. John Hodgman does not necessarily represent Microsoft in those ads - he's standing in for the hardware companies.