The Free Software Catalog
Most computers come with MS-Windows. So whether we like or not we are compelled to pay for at least that bit of software.
Once we have it, however, Microsoft offers a variety of add-ons, tools and other essential components. These tools include simple utilities, OS extensions, application programming interfaces (API's), application frameworks, virtual engines and more. Most of these tools are simply prerequisites to other software packages, e.g. DirectX is required for many game programs and the .NET frameworks are used by a variety of applications.
You must be running a genuine Microsoft Windows Operating System to acquire many of these updates and tools.