It’s simple. Quick answer is, go to Settings then Recovery, there should be an option for you to select to Go back to old Windows 7 or previous version of Windows that you’ve upgraded from.
So basically it happened to me because I have a bunch of programs software applications that work perfectly fine in Windows 7, then after upgraded to Windows 10 it no longer work. Well to be specific, the software still run opens fine, but the driver for the hardware of the software didn’t work. Basically the failure was a usb driver didn’t work in Windows 10. It have to do with signature something … I’m not sure. But, when I restored back to Windows 7 it work fine.
The restore process of Windows 7 from Windows 10 was very simple actually, a few click and I am back to the old Windows and I can continue my work. Meanwhile I contact the manufacturer of the hardware asking for a Windows 10 driver before I go to Windows 10 again.