Seems like a wishful thinking about the first stage portion of collapse. You're going to be more interested in running some obsolete version of Windows that controls some proprietary infrastructure hardware, not running calculations of whatever kind or building things from scratch.
While it is most likely a very fanciful pet project borne out of post-apo fantasy doomporn, there is one fatal fly in the ointment: In a post apocalyptic situation, who will have THE TIME (nevermind the resources) to dedicate to "operating" one such OS? Apocalypse is generally synonymous with population collapse. Many less humans to interact with means a greatly diminished division of labour and rebuilding civilisation will require first and foremost food production, 14 hours of daily work in the fields, scavenging, hunting, etc....
Taking one worker away from these (tedious) activities would likely be considered an investment that requires significant returns, results, be it only to justify this to other workers who would also like to be sat in front of a computer. Hard to justify having swapped a hard days work for some code on a computer screen.
For that kind of scenario, a lightweight Android rom with some ham-radio driver would probably be more appropriate.
That's assuming you can find the proprietary software that is needed. In some cases you're better off just cutting the proprietary bits out entirely and hooking straight into the motor controllers... or whatever else is more immediately upstream of the "business end" of the thing you're hacking.
Depends on the level of collapse, and say you get infrastructure up and running (temporarily, mind you, without manufacturing..) - what then? That's what this is for. Cobbling together the pieces left over.
