[Unter]

Для x86:

Код:

   <settings pass="windowsPE">
        <component name="Microsoft-Windows-Setup" processorArchitecture="x86" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
            <DiskConfiguration>
                <Disk wcm:action="add">
                    <ModifyPartitions>
                        <ModifyPartition wcm:action="add">
                            <PartitionID>2</PartitionID>
                            <Letter>D</Letter>
                            <Order>1</Order>
                        </ModifyPartition>
                    </ModifyPartitions>
                    <DiskID>0</DiskID>
                </Disk>
                <WillShowUI>Always</WillShowUI>
            </DiskConfiguration>
        </component>
    </settings>

Для x64

Код:

    <settings pass="windowsPE">
        <component name="Microsoft-Windows-Setup" processorArchitecture="amd64" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
            <EnableNetwork>true</EnableNetwork>
            <DiskConfiguration>
                <Disk wcm:action="add">
                    <ModifyPartitions>
                        <ModifyPartition wcm:action="add">
                            <Letter>F</Letter>
                            <PartitionID>1</PartitionID>
                            <Order>1</Order>
                        </ModifyPartition>
                    </ModifyPartitions>
                    <DiskID>1</DiskID>
                </Disk>
            </DiskConfiguration>
        </component>
    </settings>

Это я делал для существующих партиций на 1-ом и 2-ом дисках.