supressing a setup.exe launch on NSIS installer

I'm trying to silently install this file, and right now If I specify /S, it leaves out uncompressing files, but afterwards the installer calls setup.exe and it pops up. Is there some switch or something I can use to make it not call setup.exe?

if not, is there a way to open up the .exe and edit, retrieve files? I could make a program to do this if I knew how to get in

If that setup.exe installer doesn't support passing on the silent switch to the installer it executes, there's nothing you can do but unpack it and run the internal installer yourself. Use 7-zip to unpack the installer.