I know windows internals pretty well and streamlined as not what I'd call it. The layers of crud are too deep now even after their "minwin" initiative. Really, a lot of the API, even win32, is pretty nice but it has diverged from something sensible after windows NT 4. I remember running that on my dual Compaq Pentium Pro 200 with a whopping 64Gb of RAM. That was the last good windows machine I had.
Edit: I still have an old PC somewhere and some NT4 media. Hmm.... vintage non internet PC time?