Probably today in most cases it is better to buy a new state-of-art device rather than fitting WIN10 on slower &  possibly non-compatible computers designed for WIN7.  Still, Microsoft has left capability intact even as we enter 2021 as a free means to improve security & functionality for mostly home users.  For users with very powerful WIN7 computers like a tower unit, this older capability might work, esp. if users backup all data & do all the WIN10 prerequisite homework.   WIN10 is also far improved as we approach 2021, than the early versions where standards were being worked out. 

Microsoft continues to let Windows 7/8.1 users upgrade to Windows 10 for free (xda-developers.com)

Starting in 2015, Microsoft offered Windows 7 and Windows 8 users to upgrade to Windows 10 for free. The upgrade program allowed users with genuine license keys to upgrade to the latest operating system at no extra cost. While the free update program ended in 2016, it seems that the offer continues to remain valid.

How to get Windows 10 upgrade for free:

  • Make sure you are using a genuine copy of Windows 7/8.1 on your device or virtual machine.  Note that a corporate/volume licensed instance of Windows — even if it’s genuine — isn’t eligible.
  • Head over to the Windows 10 download page and download the tool to install the OS.  Alternatively, you can download the full ISO of Windows 10 from this page (may redirect to the Media Creation Tool download page if opened on Windows).
  • Open the Media Creation Tool and select ‘Upgrade this PC now’.
  • Accept the terms and conditions and choose the upgrade option where you keep your files and information. Doing a fresh install via the Media Creation Tool may not get you Windows 10 for free, so be careful!  A summary of available upgrade paths from Windows 7 or a later operating system to Windows 10 can be found here.
  • Once the installation completes, connect your device or virtual machine to the internet and open Windows Update > Activation. Click on the ‘Activate’ button if required and your PC will be activated with a digital license after it establishes a connection to the Microsoft servers.
  • In case you are unable to obtain the license, you can enter your Windows 7/8/8.1 product key and manually activate the operating system.