Do you mean boot from network F12 then Winpe then ghost?
If you do then you need to add the Winpe to Windows deployment Services under boot images, the pc dos boot for ghost should be listed under the legacy images. you need the right winpe with ghost included.
We never bothered, but we may in the near futhure as we are looking at adding the Win7 boot image to WDS for the awkward pcs that are missing all the network dos drivers in ghost.
Leon