Go Back to Windows 7 or 8.1

if you’ve upgraded a PC to Windows 10 not performed a clean install, but an upgrade you’ll have an easy option that lets you revert to the last version of Windows. To access this, open the Start menu and select Settings. Click the Update & security icon and select Recovery.

You should see a Go back to Windows 7 or Go back to Windows 8.1 option. Click the Get started button to get rid of your Windows 10 install and restore your previous Windows install. Microsoft will ask you why you want to go back