Posted November 16, 2020
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XP : Shows a login dialog box telling you to activate now. If you click don't activate it will forcibly shut down rendering the whole OS completely unusable.
Vista : Reduced Functionality Mode + can't access Personalization page. Aggressive nag screens. Can't update. Can't use Bitlocker / built-in games. Forcibly logs you out after 1hr, every hour.
W7 : Permanent watermark on desktop + can't access Personalization page. Hourly nag screens. Can't update.
W8 : Permanent watermark on desktop + can't access Personalization page. Nag screen every 6 hours. No actual restriction on usage.
W10 : Permanent watermark on desktop + can't access Personalization page. Occasional nag screen (fewer than W8). No actual restriction on usage.
So as far as running offline without ever activating goes, Windows has gradually become less hostile over time to the point it's no longer the "blocker" it once was.