You can pre-extract the installer, which I believe prevents all those DOS boxes.
Run "installername.exe /?" for the command line parameters.

You will need parms to tell it where to extract, to not install(extract only, and the destination.

something like installer -a -x -d c:\temp

Just pulling from very long term memory.

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If you want to run as system.......
You can set it to "not wait" to finish.
then run the next action as "user".
I can't recall the process name, but it is the small progress notifier in system tray.
Just check task manager.
You may also need to kill the existing process before you start the process as user.

Sorry for being a bit vague....It's been a while since I've done all of this, but the process has not changed.....