If you're worried about being forced onto Windows 10 - there are ways to prevent that from happening.

http://www.windowscentral.com/heres-how-stop-free-windows-10-upgrade-your-computer


>If this is the only way, I will first make a good backup of the entire PC. Then will see. Too back I cannot purchase and just enter some king of key, as it is done with many other software.
>Thank you.
>
>>I suggest you read the EULA. My *guess* is that you will agree to the changes being made.
>>
>>>My Office 365 is coming to end of the first year. So I need to renew the subscription. I see the button Buy in Outlook. But when I click, MS asks if it is ok to make changes to this computer. I don't trust MS as they may start upgrading OS too. Is there a way to Renew Subscription without having MS making changes to my PC?