Hi Dave,
not sure if you have done this already, but what I did was downloading the driver set for the SFF on the HP web site and that included the Vista drivers (I need always both, x32 and x64), which I injected into our WinPE 2.1 and they worked since on either platform (USDT, SFF and even CMT).
What I don't know is how you maintain your WinPE as I don't use the standard way from Symantec, but manage WinPE myself and inject drivers myself and never used the bootdisk creator for such purposes.
Since I can't attach EXE files and the driver sets are aroudn 30 MB for each (x32/x64), I won't upload them here, but if you drop me a line with an eMail address to where I can send them, I will relay them thru to you.
-BBC