If I were head of Microsoft Windows

I would make a proprietary, Posix standard kernel, and guarantee every windows application run one on that kernel. I mean, use their marketing power to define the absolute standard in kernel, they put VMWare in a hole because the Windows kernel now runs Linux applications.
If I were feeling radical, I would think about releasing the Win32 GUI under open source, unmodifiable license. Then you really do have Windows everywhere, both the GUI and the kernel. Everyone writing to Posix would be writing to Microsoft Windows. Everyone building development and other frameworks with the Windows GUI would be writing to the Windows kernel. Get them from both ends, basically capture all the Linux desktops as frameworks. Open up the Windows to the server market in a big way, taking much of the linux kernel business.