I had opened a ticket with VMWare. They had no informaiton on the "VirtualCenter-preISOConfig.exe" utility, but their solution to the update was to copy the files to the local drive.
That's what I ended up doing and it worked OK.
Afterwards (with 20-20 hindsight..) I did notice in the "readme.txt" there is a statement "VMware recommends that you run autorun.exe to install vCenter Server and its components after you extract them from the archive or iso image."
It said it was "recommended", not "required", and it didn't say why, but I guess I should have looked closer at the readme.txt....