Installing from Media is not new, but Windows Server 2008 does have a new way to create the "seed" media using a new ntdsutil ifm command. For a technet topic that explains the steps to create the media, see Installing AD DS from Media.

You can see in the topic that IFM does not help to pre-seed SYSVOL. This will be fixed in Windows Server 2008 R2. In the meantime, you can try the steps KB article 311078 to pre-seed SYSVOL.

Searching around the net, I came across these other links you might try:

Creating a Read Only Domain Controller on Windows Server 2008 Core Using the Install From Media (IFM) Option

Screencast: How to Install from Media (IFM) a Server Core Domain Controller

Install Read-Only Domain Controller on Windows Server 2008

Active Directory Domain Services: Install from (restored backup) media (IFM)

 

This posting is provided "AS IS" with no warranties, and confers no rights.