If he is really geeky, he could create a binary translator that he would then apply to all of Windows executable and library files (including those in .cab files) to get a MIPS version of Windows from the standard IA-32 version of Windows.
Patching it would be a pain. Installing software would be equally painful. Drivers would also be an issue, but I suppose he could always write his own using the linux drivers as a guide.
I imagine a job offer from Microsoft would soon follow if he went ahead with this and posted about it on the internet.