Fixed! As I said, I was starting the network install from a mounted volume that contained a folder "XPSP2" that contained the sources from my XP CD. Once I mounted the network share one folder deeper, so that the share was the root of the sources folder, this solved my problem. It must be something in the way that the DriverPacks setup refers to the path for those two files, basically assuming a CD type situation so that they have to be relative to the type of path a CD would have, i.e. "drive letter":\"sources". I just ran it with this set up and it found the files no problem.

I have been having the same problem with presetup.cmd and setup.org. I am installing from a network share that I installed the driverpacks into. I think the problem is a pathing problem. My network share is mapped as U:XPSP2\I386.... I think if I start the install with U:\I386... etc. that might solve the problem. The original copying of  the two files never happens because setup is looking for the sources one folder level up from where they are. Will give it a try and see what happens.