Mixed Authentication, ASP.Net 2.0, IIS 5.0

Can someone point me to a ~working~ example of using mixed
authentication in an ASP.Net 2.0 website?

I have been screwing around with this all day and I am no closer to a
solution. It seems to me that this sort of thing should just be "built-
in." I can't believe that after 10+ years of ASP.Net and IIS that
there isn't an integrated solution for this.

I know there must be a lot of other developers out there with this
need - integrated windows authentication for internal users, forms
authentication for external users - all in the same site. Why is this
so #!$) hard??

Why do we have to jump through flaming hoops of custom ISAPI filters
or HTTP modules spewing out javascript with redirects, and Lord knows
what else, just to support both internal and external users in a
seamless fashion?

I have been googling this all day long, and have found several
articles, most of which are several years old, and which involve
labyrinthine coding and IIS tweaking to make them work. Am I missing
something obvious here?