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