(2015-12-31)
To block the icon from showing/disable notifications:
- Navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Gwx
- Create a new REG_DWORD registry value called: DisableGwx
- Give it a value of: 1
Or uninstall the relevant Windows update:
KB3035583
http://winsupersite.com/windows-10/disabling-windows-10-upgrade-notificationNote: The ‘Gwx’ key within the registry did not exist on my home PC. I’ve uninstalled the KB3035583 update instead and will reboot PC to confirm.