For a desktop OS? I'd start by looking at windows pre-8, and then look into everything MS has done since as a helpful guide of things to avoid. While completely

For a desktop OS? I'd start by looking at windows pre-8, and then look into everything MS has done since as a helpful guide of things to avoid. While completely ignoring Linux outside of purely technical details and pretend apple and mobile don't exist. I would also remember that since i'm creating a system's OS, I should treat the internet as an after thought in the core concepts of my designs. That would be a good start.