Getting back to the question in the title, this is my experience:
If you purchase a computer from a standard OEM (Dell, HP, etc, etc) with Windows installed, it will not just work. In fact, day to day usage of the computer is a very poor experience. This is because of all of the bloated crapware and out of date drivers that they preinstall. Boot up times are sluggish. Software installation is error prone. The registry is flooded with useless nonsense. There are too many useless processes and services running.
If you purchase a computer and do a fresh install of Windows plus up to date drivers, it will just work. Boot up times are fast. Application launch times are fast. Software installation is much less error prone (excluding the occasional poorly written installer). Very few processes and services are running.
The vast majority of people experience Windows through a crapware infested PC courtesy of their friendly neighborhood OEM. I am of the strong belief that this is a big contributing factor to the perception that Windows PCs do not "just work" as well as, say, a Mac which does not come out of the box in a corrupted state.