Vista - Windows Deployment Services Question

I'm trying to get a handle on setting up WDS and I must be getting confused
by the various passes and such.

My client machine PXE boots from the server just fine and immediatly begins
booting the Vista WinPE. Once the backdrop loads I'll get an error windows
stating:

"WdsClient: An error occured while starting networking: a matching network
card driver was not found in this image. Please have your Administrator add
the network driver for this machine to the Windows PE iamge on the Windows
Deployment Services server."

Okay, so how do I do that? When I use the Vista DVD to build the machine
the NIC drivers get installed correctly, so I had thought that they were
built in all along. Do I add them via the unattend.xml file during the
"windowsPE" phase or am I heading off in the wrong direction?

Thanks