Step 1: How the Windows 10 upgrade works
When you upgrade to Windows 10 from Windows 7 or Windows 8, your existing Windows installation is saved, rather than deleted. Those old files then stay on your PC for a month (unless you delete them manually), after which Windows 10 assumes that you’re happy with the way it works and deletes the files to free up several gigabytes of hard drive space. These files are also used to restore your previous version of Windows if you want to uninstall Windows 10.
Step 2: Check if you can uninstall Windows 10
To see if you can uninstall Windows 10, go to Start > Settings > Update & security, and then select Recovery in the left of the window.
Step 3: Start the uninstallation
Look in the right of the window and you should see an option for Go back to Windows 7 or 8. Click the Get started button below to begin the uninstallation process.
Step 4: Wait while the uninstallation completes
Uninstallation will take a while and Windows 10 will ask why you’re removing it. After a couple of warnings, your PC will restart and Windows 10 will be uninstalled. This can take anything up to an hour, depending on your PC, but there’s nothing you need to do while it’s in progress.
Step 5: Check everything is still working
When Windows 10 has been removed, you’ll be back at the Windows 7 or 8 Desktop. It’s wroth checking that everything is working normally at this stage and that your important files are intact. You will also need to install any software you installed under Windows 10.
Step 6: Uninstalling the Insider Preview
If you upgraded Windows 7 or 8 using the Insider Preview (beta) version of Windows 10, you probably won’t have the option to uninstall it. Windows 10 only keeps the last set of operating system files when it gets updated.
So if you used Windows Update to get the final ‘build’ (i.e. version) of Windows 10 on 29 July, you’ll now only have the option to revert to the previous build of Windows 10.
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