The only thing you need Windows for are games that simply cannot be made to work in Linux (which is very few).
If you are truly paranoid about Microsoft, or paranoid that 99% of PC malware targets Windows, or even if you hate the PC acting like the personal assistant you never asked for and don't want, then use Ubuntu. It is FREE. It can be installed and re-installed ad infinitum, and requires no CD Keys to do so. It's user-friendly, easy to install, updates itself automatically, and has an "app store" with hundreds of world-class applications that can be installed for free. And (at least at this point) it does not collect information or attempt to act as a personal assistant.
There are downsides, of course. Commercial software (if you absolutely must use it) tends to be Windows or Mac-specific, and much of it takes real skill to get working in Ubuntu, and sometimes simply will not work.
My recent experience with Guitar Pro 6 is representative. They claim to have a Linux version, but to install it under Ubuntu, I had to unpack their installation file, rename the app to all lower-case, remove a dependency that was stated incorrectly, install version 0.9.8 of openSSL into the usr directory to make it happy (even though Ubuntu includes openSSL 1.0.0, which would work perfectly fine), and install a few other unstated dependencies. It was a nightmare 5 or 6-hour struggle, all because my stepson bought a $59 software package that my wife REALLY wanted to use. There is a "tuxGuitar" work-alike that is free, and even imports and exports Guitar Pro files, but she refused to go that route. I did eventually get it all working, but for them to say that their product works in Linux borders on dishonesty. It looks as if they had it working for one version of Linux, without following any of the proper best practices for packaging a product for distribution, or even bothering to learn what those practices might be.