Yup, I honestly expected an article about the build environment and stuff like build times. Can you compile Windows from scratch on a regular development machine in a decent time frame? I guess it depends on whether you're thinking of the Windows kernel or Windows the desktop environment.
Though it's a pretty old, this Microsoft presentation from USENIX 2000 describes how Windows NT development evolved from NT 3.1 through Windows 2000, including details about source control and build machines.
I agree that they could have taken a different angle with the post title, even though it isn't open source. I'm sure many would be interested in hearing about how they build it. I would.
