Hi everyone.
Recently, during a Siebel Web Client install, I faced an odd error when launching Oracle Universal Installer.
The error was: CreateOUIProcess(): 5
After some research, I figured out that this is caused because of my temp folder.
By default, my TEMP environment variable is configured to %USERPROFILE%\AppData\Local\Temp, which was causing the error in the installation.
In my case, I changed this variable to D:\temp and, after that, I was able to lanch the installer as expected.