[Dailydave] luckily, there are no dumb questions

[dan at geer.org]

Luckily, there are no dumb questions or this would
likely be one.

How is it so that MS Windows uses only Rings 0 & 3?
An engineering answer, a marketing answer, and/or
an historical answer would be welcome.  Don't know
why I never thought to ask before, but I'm asking
now.  (And if I'm really wrong, please tell me what
uses 1|2.)

Bemusedly,

--dan