Using Host Headers in IIS7 / Why is the host headers text box disabled?

If you want to run two sites on the same port you will need a Wildcard Certificate. Eath site will be assigned a different host header (= URL) in IIS (e.g. site1.yourdomain.com and site2.yourdomain.com).

What if the host name text box remains disabled although I have a Wildcard certificate?

The friendly name of the Wildcard certificate needs to start with an "*" (e.g. *.yourdomain.com) as you can read here.

You can still use the command line though to set the host headers appropriately.

How to grant permissions to the Network Service account of another machine?

1. Create a security group in Active Directory
2. Add the computer account to the group (DOMAIN\MACHINENAME$)
3. Grant permissions to the newly created security group.