https://www.theregister.co.uk/2017/09/06/microsoft_extends_free_windows_10_s_to_win_10_pro_upgrade_offer/

Microsoft has quietly extended a free upgrade offer that will allow some buyers of Windows 10 S to move to Windows 10 Pro, a move that suggests buyers aren't entirely happy with the cut-down version of Windows restriction on running apps sourced from beyond Microsoft's own Store.

Windows 10 S is a cut-down version of Windows that behaves an awful lot like Chrome OS.Microsoft launched the product in May 2017, suggesting it would be a fine laptop for mass deployments in schools or perhaps even in businesses that don't need full desktops for some workers.