Windows Setup allows you to provide an answer file for a unattended install. Windows 2000/Windows XP had the winnt.sif but Windows Vista, Windows 7 and Windows Server 2008 allow you  to provide a Autounattend.xml file. If you follow the right steps with SIM (Windows System Image Manager) and add the components the setup needs you can build a file which perform a automatic installation without any input during the setup phase.

Well I build such a Autounattend.xml file I run into the problem when the Windows Setup started I needed to choose which version of Windows Server 2008 R2 I wanted to install. This step I wanted to skip and really have automatic installation.  To make that happen you need to add InstallFrom into the XML file.

<ImageInstall>
               <OSImage>
                    <InstallFrom>
                        <MetaData wcm:action="add">
                            <Key>/IMAGE/NAME</Key>
                            <Value>Windows Server 2008 R2 SERVERSTANDARD</Value>
                        </MetaData>
                    </InstallFrom>

                    <InstallTo>
                        <DiskID>0</DiskID>
                        <PartitionID>1</PartitionID>
                    </InstallTo>
                    <WillShowUI>OnError</WillShowUI>
                </OSImage>

</ImageInstall>

Make sure you query the WIM file with imagex.exe /info d:\sources\install.wim and insert that for MetaData Value (marked in RED).