Originally posted by OriginalPhoenix
Win95 and Win98 don't really have a "pure" DOS either, but a stripped-down version for backwards compatibility mode. WinMe has much the same thing, it's just more difficult to get into it. And FWIW, WinMe is considered part of the Win9x line.
Not entirely accurate. Windows 95/98(SE)
do contain a pure DOS. MS-DOS 7.0 and 7.1 respectively. These dosses(?) are no less DOS than MS-DOS 6 was. They can be booted on their own, don't need any part of Windows to run. Windows just doesn't bring all the old DOS utils anymore, but the DOS is still the same (with added support for MFAT and FAT32 of course, and probably some other new stuff as well).
While Windows 95 relied on the MS-DOS command interpreter (command.com) to run, Windows 98+ do not, but they still use the MS-DOS bootstrapper and kernel contained in IO.SYS.
Windows Me also contains a "pure" DOS (MS-DOS 8.0). But they changed IO.SYS so it was no longer possible to boot it in real mode. The version of IO.SYS that ends up on WinME boot disks of course does allow this.
Windows NT/2000/XP were never build on DOS to begin with. They contain a command.com (which calls itself Microsoft Windows DOS when you start it manually) which gets started automatically when you run a real mode MS-DOS 16-bit program from CMD.EXE. Command.com in WinNT is not real DOS, just a command interpreter that exhibits behaviour closer to MS-DOS than cmd.exe provides. Behaviour that MS-DOS programs expect. Most notably it runs inside the NTVDM.EXE to provide old fashioned MS-DOS interrupt call support, and in Windows XP also gives (lousy) Sound Blaster emulation. The MS-DOS kernel (IO.SYS) is nowhere to be found in NT.
So in summary: Win9x/Me runs on the MS-DOS kernel but starting Win98 doesn't require command.com anymore other than to provide console services. WinNT/2000/XP doesn't run on any other kernel than the ntkernel itself (which was written from scratch, and not based on MS-DOS in any way) and provides MS-DOS compatibility through NTVDM.
I think MS altered WinME to make MS-DOS impossible to start to prepare people for the switch to XP and the phasing out of MS-DOS altogether.