I purchased Windows 8.1 around 2 years back, I have the original DVD, and installed it on my laptop. Later, I upgraded it to Windows 10 around 8 months back. I want to completely remove everything from my laptop and install Linux OS on it. Before doing this, I want to make sure that I've somehow backed up my Windows 10 (OS only, not data) in some sort of DVD form. So that, in future when I want to install Windows again, I can have my Windows 10 back, instead of old Windows 8.1.

Is it possible?