There is a way to undo the install and revert back to your original Windows edition.
But, it must be done within a month of the initial install.
http://www.howtogeek.com/220723/how-to-uninstall-windows-10-and-downgrade-to-windows-7-or-8.1/
http://winsupersite.com/windows-10/how-revert-back-your-previous-os-after-windows-10-upgrade
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I made a Macrium Reflect image of my Win7 OS before going through the Win10 upgrade process, just in chase. I am still going to explore 10 for a while, since I have it on an extra hard drive.
For regular stuff, I still am using Win 7 on another hard drive.
My brief experience with Win 10 — I HATE IT. If it had a classic theme, it might be usable.