As far as I know, the GUI of the linux distros runs over a non-graphic kernel. You can see the ‘command prompt’ loading programs and devices while the system starts. Moreover, you can do any task in the command prompt. I wonder if MS Windows is something like that, just a GUI running over a ‘core’ OS.
Windows 1.x, 2.x, 3.x ran on top of DOS, Windows 9x could be considered DOS-based, and the NT series, as well as XP, Vista, 7 and 8 have a command prompt for compatibility but do not “run on top of” anything.
Wikipedia has a good background: