One's operating system is their base from which all else is possible. Choosing the right one is important not just functionally, but with respect to one's privacy and anonymity.
The Linux/Unix category of operating systems provides a great variety of choice in the form of "distributions". More experienced readers likely have their favorite distribution already. For the neophyte, we recommend Linux Mint: it is as close to Windows as can be had. Linux provides the user with tight control of their entire operating system, since *nix OSs are open-source and free, and not proprietary, like Windows. All cybersecurity measures mentioned throughout DHitMA can be performed just as well on Linux, and oftentimes with greater ease than can be done on Windows.
We reiterate that we do not recommend Windows for an operating system. There is reason to believe that Windows is classifiable as spyware. Windows may be used where one requires access to its specific functionality (like playing video games). This should only be undertaken by one who cannot afford a more capable computer, or is unwilling to work with Linux. There are several steps that need to be undertaken if Windows is to be used.