Windows Server doesn't come with IIS enabled by default, make sure the
Web Server (IIS)\Web Server role has been added.
IIS's web server role doesn't include ISAPI Extensions by
default. Add the feature
Web Server (IIS)/Web Server/Application Development/ISAPI Extensions to the role.
For the Proxy Module with the authProxy:
The Proxy Module with authProxy machine will need to be added to Internet
Explorer's Local Internet zone, so if you have a server already
listed there, you may want to use it.
This must be a separate machine from the Search Appliance,
and the machine the Proxy Module is installed on must be a member of
the Active Directory domain.
Ensure that the machine that the authProxy is being installed on is
a secure machine. Because the Proxy Module is dealing with
authorization functionality, a user with Administrative privileges
could potentially tamper with operations.