Every once in a while, someone sends me mail (or a pointer to a blog post) and asks "Why can't you guys do something like that?". The implication seems to be that Windows would be so much better if we simply rewrote the operating system using technology <foo>.
And maybe they're right. Maybe Windows would be better if we threw away the current kernel and rewrote it using <pick your favorite operating environment>. I don't know, and I doubt that I'll ever find out.
The reason is that making any substantial modifications to an operating system as large and as successful as Windows is hard. Really, really, really hard. You can see this with Vista - in the scheme of things, there were relatively few changes made to existing elements of the operating system (as far as I can tell, the biggest one was the conversion from the XP display driver model to the Vista display driver model), but even those changes have caused a non trivial amount of pain for our customers.
Microsoft, Windows, Article