Implement Windows and Forms Authentication

[Rafael Veronezi]

I would like to know if there's a way to implement both Windows Integrated
and Forms authentication in my Asp.net application. It's an Intranet
application wich I would like to enable from inside and outside access...
It would work in the following way...
When the authentication is requested, the system would check if he can
authenticate by windows user accounts/password. If it doesn't, he would show
a authentication request, using simple forms authentication..
Don't know if it's the best way...
Don't even know if I can implement something mixed this way...
I sometime heard about methods of implementing authentication directly from
the IIS, this way I don't know how it would differs from implement a Windows
Integrated authentication from ASP.Net... I'm in doubt...

Thanks,
Rafa