If you are running Windows 7 , 8 or 8.1 you may want to stick with your operating system and not make the move to Windows 10.
There is currently a piece of software that will assist you with this the – GWX Control Panel – which it claims will help you do this.
It will also stop the Windows 10 reminder.
Remember Microsoft may in the future block this piece of software and you run this at your own risk.
More information and details on how to do this can be found here at the How To Geek Site : How to Stop Windows 7 or 8 from Downloading Windows 10 Automatically