I had to install Oracle9i Discoverer Desktop 126.96.36.199.01 and afterwards Discoverer Patchset for Desktop-only 188.8.131.52.01.
Unfortunately responsefile creation is not supported by the Universal Installer that comes with the installation. You have to edit the responsefiles located on the source at Stage\Response
As usual the setup exits before the end of the installation. I used taskwait to monitor first setup.exe and then javaw.exe. (Setup.exe forks into javaw.exe and then quits).
Important note for silent removal of the product:
After you have applied the patch, you cannot uninstall anything with the Universal Installer on the local disk, nor with the one in the source of Discoverer. Only the setup.exe located in the source of the patch will work.
You can use the same rsp files you used for installation for removal. Make sure to uninstall the patch first.