When I installed Opencascade for the first time with the command
java -jar setup.jar I could change the installation directory of opencascade.
I had to reinstall opencascade because I lost some files during the compilation.
But when I try to reinstall opencascade I could not choose the directory because the installer did not show the first menu where you can choose the directory because it thinks that this is not a new installation.
I find the solution : if you erase the file : "vpd.properties", the installer works as if it is a first installation.
Hope this will help somebody in the future.