I need your help to prepare a forwarder script (silent installation) that will be on my Windows (empty installation).
The comment from ddrillic should get you on the right track.
On top of that, I'd suggest to add some code to the script to generate a random password for the admin user and set that through the CLI after install.
I have been using the following -
msiexec.exe /i splunkforwarder-6.5.1-f74036626f0c-x64-release.msi INSTALLDIR="E:\opt\splunk" DEPLOYMENT_SERVER="<host>:8089" AGREETOLICENSE=Yes SERVICESTARTTYPE=auto LAUNCHSPLUNK=1 /quiet