To reverse your right to get Windows 10 upgrade for your existing windows 7 or 8 operating system you can follow the steps given below:
You need to go in your control panel.
After you visit Control Panel you will be able to see Windows Update, navigate to Windows Update and click on it.
After Windows Update got open you will be able to see a message like “Windows 10 is coming soon. Reserve your free upgrade to Windows 10 today”.
Below message you will be able to see reserve button, navigate to reserve button and click on it.
After clicking a window will get open which will say ” All done for Now. There’s nothing else you need to do. You’ll get a notification on your PC or Tablet when Windows 10 is ready for you.”
After some days when you get a notification like Windows upgrade is ready to install that time you need to click on that notification and click on install.
Note: The last date of the free upgrade is 29 July 2016.