Windows Deployment Server and Re-Re-Imaging via PXE Boot

I'm just getting the hang of trying to configure/use Windows Deployment Services (WDS) to image Windows 7 workstations on our network.

I have the WDS server configured so any machine can request an image, but the administrator must authorize the configuration. This way we would minimize accidental (or malicious) re-imaging of computers on the network.

For the initial setup, I configured the base Windows 7 install and boot images then hooked up a testbed Dell machine. Booted the Dell with PXE boot, it started the PXE boot, and went back to the WDS server to authorize ID 1 machine. No problem, the Dell booted to Win7 setup and started the whole configuration process.

Got all done and started going through instructions to create an image WIM file on the master; Sysprep with the generalize option completely hosed the staging client. After many profanities, I decided to start from scratch again.

Rebooted the client with PXE boot, and this time it saw the WDS server and started the re-imaging process again without me authorizing it.

This makes me think that if individuals on the network managed to PXE boot an imaged machine, the machine will allow them to re-image it without authorization.

Is this the case?

If so, is there a way to clear out the already authorized ID's/MAC's from the WDS server?

Using Windows Deployment Services on Windows 2008 Server.