[jedieaston]

I don't know that Windows would run without the licensed code, or at least Explorer. If they didn't bother to write their own ZIP library (or use an open-source one) then they probably licensed a lot of other stuff that one would expect a first-class desktop is to have, making it unusable without a bunch of developers fixing it (when their company would probably buy them a license anyway).

If it was released without the third-party code, then it'd be a research project, which'd be pretty neat but not something most probably expect from "Windows is open source".

[gsnedders]

Java, when open sourced, couldn't run with purely open code (it relied on some binary blobs Sun provided); it's plausible MS could do similar. There would likely be a fair bit of interest in replacing the binary blobs in Windows.