I am fairly certain that the phase used after the boot.wim/WDS process is used is not WinPE. It is Windows Setup. But, technically I believe you aren't supposed to deploy (actually, you do not even mention which OS you are using!) OK so anyways, you aren't supposed to deploy Vista or 7 with this method to every machine. You can, by all means, go for it, but MS documentation (at least what I have) say you use your Unattend install for the Master Image. Hence you only install it once. Then you would use sysprep (and its XML) to redeploy that image to other machines.