Just in case TurboTax forces a change from Win 7 to Win 10 after January 2020 when MS stops supporting Win 7, and you don't have a Win 10 PC yet, it is still possible to download and install Win 10 LEGALLY without purchasing a license key (as of yesterday 11/28/2019 - I checked) using the MediaCreationTool.
See this article at How-To Geek for more info on how to do that:
http://www.howtogeek.com/244678/you-dont-need-a-product-key-to-install-
and-use-windows-10/
This article also describes the process:
https://www.intowindows.com/download-windows-10-media-creation-tool/
The installation of Win 10 will nag you for a license key, but you can still install it without one and without activating it after installing.
Nobody knows how long MS will continue to allow installation of Win 10 legally without purchasing a license key, so this could change at any time.
You may not want to abandon Win 7 for Win 10 on your PC (I wouldn't), so you could set up a dual-boot system for Win 7 and Win 10 on your C: drive if your system has the space. I have done that in the past without too much trouble. Win 10 will set up the boot so that Win 10 is the default and there is no wait for operator input, but the free program EasyBCD can help you correct that easily so that Win 7 is the default and the system will wait for the user to select the OS to use before proceeding.
Win 10 will operate on as little as about 25GB, however, without more space, updating Win 10 monthly gets troublesome, so I used about 1/2 of a 500GB SSD when I tried it - the other half left for Win 7.
This article will tell you how to do that:
https://www.howtogeek.com/214477/how-to-dual-boot-two-or-more-versions-
of-windows/
The limitations on using Win 10 without activating it with a license key are essentially cosmetic - you can't "personalize" it.
However, you can still install and run TurboTax 2019 without activating the Win 10 installation.
Of course if you decide you like Win 10, you could install it over Win 7 and activate it (so-called "up-grade"). I have not tried that, but some people have reported that you can still "upgrade" to Win 10 for free from Win 7 as of earlier this year. (They give it away free because of the treasure trove of data they collect form your usage, and presumably monetize, if you don't turn off the data gathering - plenty of articles on line about how to try to do that.)
Follow all recommended procedures to backup your important data files before mucking about with the operating system in case of catastrophic failure. Also make a system image of your C: drive as well in case you need to revert back to your existing operating system.
Good luck!
