Updating to 8 10
That means that computer came with a product key that allows you to use Windows 7 or 8.1 on it.
If you can’t downgrade to your old version (maybe it’s been to long, or maybe something went wrong with your downgrade attempt), you’ll have to perform a clean install of Windows—something PC geeks often do on new computers, anyway.
In the Disk Cleanup window, click the “Clean up system files” button.
In the list of files Disk Cleanup can remove, find the “Previous Windows installation(s)” entry, and can see just how much space it’s consuming on your hard drive.
Download the Windows installation media and burn the ISO file to a disc or copy it to a USB drive using Microsoft’s Windows USB/DVD download tool.If you’re sure you don’t want to go back to your previous version of Windows, use Disk Cleanup tool to remove those files and immediately free up space.Assuming you have an old computer you upgraded to Windows 10, that computer previously had Windows 7 or 8.1 on it.RELATED: You’ll have to find your PC’s product key if you do this.On a Windows 7 PC, examine your PC for a “certificate of authenticity” sticker with a key on it.