Hi Iva... If Your OS is Windows and you don't want that your PC to start update whenever you are switching it on or off or using it then you can manage it yourself. Windows has given that option in your control panel.
Go to the control panel and manually OFF the online update option in "system and security" and then it wont update your system till you manually set it ON.
You can turn it ON if someday you feel that you want the updates to be downloaded and installed in your system.
Just a Advice Iva.