If you still want to take advantage of the free upgrade offer to Windows 10, make sure you upgrade your Windows 7, Windows 8.0 or Windows 8.1 before end of July 2016.
Read more at https://blogs.windows.com/windowsexperience/2016/05/05/windows-10-now-on-300-million-active-devices-free-upgrade-offer-to-end-soon/#eZybh584vYuFeQfJ.99
If you are still on the fence about upgrading, you have some options:
First, you could create a system image of your Windows 7 and Windows 8 installations:
Windows 7: http://www.notebooks.com/2009/10/24/how-to-backup-your-installation-of-windows-7/
Windows 8/8.1: http://techingiteasy.wordpress.com/2012/10/29/how-to-backup-your-windows-8-installation/
Perform the upgrade to Windows 10:
- How to: install Windows 10 from within Windows 8.1 or Windows 7 using Windows Update
- How to download official Windows 10 ISO files
- How to: upgrade from previous versions of Windows using Windows 10 ISO file
Users running Windows 8.0, released in 2012 or Windows 8.1 released in August 2013, you will need to use the Windows 10 ISO file to perform a manual upgrade. The Get Windows 10 app does not work on those older versions.
Ensure your computer gets the Digital Entitlement:
Start > Settings > Update & security > Activation:
Learn more about troubleshooting activation: How To troubleshoot Product Activation in Windows 10
About Digital Entitlement:
What will happen is the hardware (your PC) will get a digital entitlement, where a unique signature of the computer will be stored on Microsoft Activation Servers. The Windows 7 Professional genuine license will be exchanged for a diagnostics key.
Anytime you need to reinstall Windows 10 on that machine, just proceed to reinstall Windows 10. It will automatically reactivate.
Backup your Windows 10 installation as a system image: warning, make sure you change the machine name before creating a system image or it will overwrite the initial system image you created for Windows 7 or Windows 8/8.1
- How to: Create a system image in Windows 10
- How to restore a Windows 10 system image to an existing or larger storage device
Rollback or restore your Windows 7 or Windows 8 system image (I personally recommend restoring the system image, it is so much faster)
How to: Rollback to a previous version of Windows from Windows 10
Once you rollback, you can use one of the following options to block the Get Windows 10 (GWX) app:
Option 1: How to Disable the Get Windows 10 Update GWX App Completely
Option 2: Stop the Windows 10 Upgrade with Never 10 or the GWX App Itself
If and when you decide to upgrade to Windows 10, or restore the system image you made in the future, you will be able to activate the OS. As long as you don't make any significant hardware changes such as a motherboard upgrade, Windows 10 should automatically reactivate
.
Resources:
How to Prevent Automatic Upgrade to Windows 10
Instructions: What to do if your system is automatically upgraded to Windows 10?