He's right. Windows 1.0, 2.0, 3.0, 3.0, 3.1, 3.11, 95, 95 OSR2, 98, 98 SE, ME, are all graphical shells running on top of DOS. They have had additional 32 bit multimedia bindings such as WinG and DirectX grafted on top to bolster performance. But they are not OS'es. They are graphical shells.
Win XP is the first consumer operating system Microsoft has produced since MS-DOS 6.22. Between MS-DOS 6.22 and Win XP, Microsoft's only consumer level products have been a series of graphical shells. Versions of Windows based on the NT kernel, however, are proper OS'es. These have until now been targeted exclusively at the enterprise and business markets.