Dear Micha & Auge,

Thank you very much for all your kind help. I tremendously appreciate it. Thank you 1000 times.

Is my understanding below correct?:

1. For the 1st forum, I do the installation in a normal way.
(e.g. www.mydomain.com/1st-forum/)

2. Then, I copy the whole directory, and re-name for the 2nd forum.
(e.g. www.mydomain.com/2nd-forum/)

3. I "manually" modify the db_settings.php file as explained by Auge for 2nd-forum.

4. I "manually" copy tables from 1st forum, and with another table prefix, past the tables in the same database for the 2nd forum.

Do I understand correctly?

Even if my understanding is correct, both directories 1st-forum and 2nd-forum contain the whole script, so it is not multi-site, but just sharing the same database...?

Do I understand wrong?

Sorry for lack of my understanding, but I am not really a technical guy... Can you please help?