I'd have thought that there should be answers to this on Microsoft-forums / Sysprep-centric sites?
I'm not trying to be a prick or anything - 'tis just that this is a "general sysprep issue" so I'd expect that other folks must've run into this as well. I can't help you much here either, what little fiddling I did with Sysprep I had the luck of using signed drivers.
Sysprep-specific forums would be the first place I'd be looking for, to be honest.
Hope this helps a little bit :).
LANDesk EMEA Technical Lead.
Change the entry "DriverSigningPolicy" to "Ignore" in unattended.txt (or winnt.sif)