@dosnostalgic let's be fair: Windows wasn't letting you "boot into the legacy OS", it was just letting you quit out of the shell, because at the time, it was literally just a fancy GUI shell for DOS, and remained so (for home users, enterprise users got NT in the early 90s) until Windows XP
@vinesnfluff No. Windows 9x was not "just a fancy GUI shell for DOS". In fact it was sort of the other way around. It was a full on standalone OS that had legacy DOS support fully integrated in its kernel. But if you wanted an actual MS-DOS you had to reboot. There was nothing to quit to, as DOS 7 that was used as a bootloader was completely gone by the time Win9x was running.