Here is a sample of what I had working that I could find. I think I also had trouble with the earlier installers

essentially run this from the commandline:

13064_HighBoots3ForV4_1.0_dpc.exe --optionfile options.txt

and then the contents of the options.txt are:

unattendedmodeui=minimal
debuglevel=4
mode=unattended
debugtrace=debug.txt
accept_license=yes
uninstall_previous=no
installdir_content=C:PoserRuntimeVictoria 4 Clothes
create_uninstaller=no
create_startmenu_shortcuts=no

Once you're comfortable with the above, then you can write a batch file that runs through all the exe's in a single directory.