If you are running Microsoft Windows 7 or Windows 8.1 and you are eligible for the free upgrade to Windows 10, then you most likely have the Windows 10 Upgrade icon in your system tray. If you do and you want to remove it, for various reasons, then I have a couple ways to do so.
The first method is to uninstall Windows update KB3035583. This update provides all the files for the Windows 10 upgrade process (Gwx.exe and needed files). Once removed restart your computer then run Windows update and hide the update to keep it from installing again.
Please Note: Editing your registry can cause problems, as such I can not be held responsible if you make a mistake or this edit doesn’t work for you. Do the following at your own risk.
The second is to edit your registry.
Open regedit and navigate to the following key:
Create a new key under Windows key and set its name as GWX
So the final key path would be:
Now select GWX key and in right-side pane create a new DWORD DisableGWX and set its value to 1
Close Registry Editor and restart your computer to take effect.