Windows 7

Windows 7 remains genuinely in use on a real population of older PCs -- specifically machines too old for Windows 10's requirements, in regions or contexts where hardware isn't regularly replaced, or running specific old industrial/embedded software that was never updated. Unlike Windows 10, there is no remaining official path to get security patches for Windows 7 at all anymore: mainstream support ended in 2015, extended support in January 2020, and even the paid three-year Extended Security Updates program available to Pro/Enterprise customers ended in January 2023. Microsoft's own current guidance for anyone still on it is simply to upgrade the hardware or move to Windows 11 where the hardware allows it -- there's no download page to link to because Microsoft no longer distributes it.