We had no rights to distribute exe files (patched GothicMod.exe and Gothic2.exe). This is why you should install patches before installing SP.
Administrator rights are required because the installer disables DEP and does some manipulations with the files. Without administrator rights this may not work.
Also it still remains a mystery to me why you are asking for administrator rights so zealously and not share the files in the archive?
Yes I tried to install 1.08k kit and also 2.6 - the same story, doesn't installing.
Why did you not just share the files in archive? The game doesn't installed in "program files" and there is absolutely no-need admin rights for that
It's just extremely strange story for me with your installer :|