<DirectoryRef Id="TARGETDIR">
      <Component Id="CRegistryEntries" Guid="*">
        <RegistryKey Root='HKLM' Key='Software\Acme\Foobar 1.0'>
          <RegistryValue Type='string' Name='InstallDir' Value='[INSTALLDIR]'/>
          <RegistryValue Type='integer' Name='Flag' Value='0'/>
        </RegistryKey>
      </Component>
    </DirectoryRef>

To support such construction:

    <DirectoryRef Id="DirMenu">
      <Component Id="CShortcut" Guid="*">
        <Shortcut Id="ApplicationStartMenuShortcut"
                  Name="Remote viewer"
                  Description="A SPICE/VNC client"
                  Target="[INSTALLDIR]\bin\remote-viewer.exe"
                  Icon="IcoVirtViewer"/>
        <RemoveFolder Id="MENUDIR" On="uninstall"/>
        <RegistryValue Root="HKCU" Key="Software\VirtViewer\remote-viewer-shortcut" Name="installed" Type="integer" Value="1" KeyPath="yes"/>
      </Component>
    </DirectoryRef>

The idea is to avoid including the same file multiple time and having
the same element multiple time defined.