...and there is an alternative to that pretty crappy webadmin application. If you go to IIS management console (Control Panel/ System Administration/ Internet Information Services), and open the properties of your virtual directory, there you should see an extra tab: ASP.NET.
In first instance it allows to select the version of .NET framework on which the web application is intended to run. Further, after clicking the "Edit Configuration" button, we see amongst others the whole goodness related to autorization and authentication services!
Now, I only noticed another problem related to the infamous Beta1->Beta2 leap... Namely, after installing Beta2 that ASP.NET tab, already present in Beta1, is gone. It's again so that some stuff is not properly removed/unregistered when Beta1 is uninstalled. To fix it:
0. Close IIS management console if you have it now open.
1. Delete registry keys responsible for enabling this extra tab, that still refer to a non-existent Beta1:
HKEY_CLASSES_ROOT\CLSID\{7D23CCC6-A390-406E-AB67-2F8B7558F6F6}
HKEY_CLASSES_ROOT\CLSID\{FD5CD8B1-6FE0-44F3-BBFB-65E3655B096E}
HKEY_CLASSES_ROOT\CLSID\{FEDB2179-2335-48F0-AA28-5CDA35A2B36D}
The easiest would be just to find those guids via CTRL+F...
2. Go to C:\WINDOWS\Microsoft.NET\Framework\v2.0.50215 folder
3. Re-register .NET 2.0 into IIS, by executing the command
aspnet_regiis.exe -i
4. Open IIS Management console, go to virtual directory properties, now the tab is visible!
Tom