.cmd files work, because I made my DetachedProgram = "%systemdrive%\install\wpi.cmd"
WPI.CMD:
start %systemdrive%\install\wpi\wpi.hta
and that executed. At T-39 minute, it brought up an "Open With" dialog box, asking which program I would like to use to execute wpi.hta, but Microsoft Application Host wasn't in the list (and obviously no registry entries to set .hta files as applications).... At first I stuffed around adding the required registry keys to the hive files, but I couldn't get the syntax correct, so then I stuffed around with a batch file that would add the required registry settings, something like this:
WPI.CMD
@echo off
if %systemdrive% == C: goto :c_drive
if %systemdrive% == D: goto :d_drive
goto :error
:c_drive
reg /import %systemdrive%\install\imports\import-c.reg
goto :end
:d_drive
reg /import %systemdrive%\install\imports\import-d.reg
goto :end
:error
echo Must have been too lazy to add more drives. %systemdrive% is not supported.
goto :veryend
:end
start %systemdrive%\install\wpi\wpi.hta
:veryend
i dumped mshta.exe and reg.exe in my $$\system32 folder.... for the import-c.reg, import-d.reg etc, I went into regedit and searched for all ".hta", "htafile" and "mshta.exe" references I could find and exported what looked like the correct stuff, I just changed the drive letter for each of the registry files... however, this didn't fix the problem....
in the end it didn't work, but i felt i was getting close... several times the command prompt window would stay up on the screen but the .hta file would not execute...