Scripting

I am trying to run windows 7 script installation with 1 fixed SATA drive and 1 usb drive present (for backup purpose). The setup failed with error "windows 7 cannot locate the disk and partition specified in unattented"... or "setup was unable to create a new system partition..." The error depends on how I configure <ImageInstall> in the Unattend.xml. Setupact.log shows that windows 7 is failed because of trying to install into the USB drive (Why it doing that??)

Here is the part in xml for installation drive: Please note I have a post install script to format the drive 0 (SATA drive) with 2 parts for the installation. and this drive is available when the installation begin.

 <ImageInstall>
        <OSImage>
          <InstallToAvailablePartition>true</InstallToAvailablePartition>
          <InstallFrom>
            <MetaData>
              <Key>/IMAGE/Name</Key>
              <Value>windows 7 enterprise</Value>
            </MetaData>
          </InstallFrom>
        </OSImage>
      </ImageInstall>

or

<ImageInstall>
         <OSImage>
           <InstallTo>
             <DiskID>0</DiskID>
             <PartitionID>2</PartitionID>
           </InstallTo>
           <InstallToAvailablePartition>false</InstallToAvailablePartition>
           <WillShowUI>OnError</WillShowUI>
           <InstallFrom>
             <MetaData>
               <Key>/IMAGE/Name</Key>
               <Value>Windows 7 Enterprise</Value>
             </MetaData>
           </InstallFrom>
         </OSImage>
       </ImageInstall>
 Anyone has similar issue?