Hello, I don't understand why you recommend to delete setup.php after the first installation. Once done, I don't see how to login and administer my galleries.
So I am trying to reinstall setup.php via ftp and I get this message when I connect the url mywebsite/zenphoto folder/zp-core/setup.php:

Internal Server Error. The server encountered an internal error or misconfiguration and was unable to complete your request.

What should I do? Thanks!

setup.php is used for setup only, and removed afterwards for safety reasons.
To administer your gallery you need to use zp-core/admin.php

zp-core/admin.php returns the same Error 500 (Internal Server Error).

Here is what I did yesterday: I wanted to create a copy of my gallery in French, as multi language doesn't work on my server. I duplicated my zenphoto folder on my server, gave the new folder another name and was about to duplicate and rename the database when the original installation stopped working. My htaccess is correct in both installations.

tks

Something is not setup correctly. Internal server errors are most caused by a wrong or missing htaccess file while trying to use mod rewrite urls. If it is not that there is something else. You should look into your server error log.

Error 500 can also be a temporary hosting problem.
I don't know which is your hosting service, but some free or cheap hosts are rather notorious for their frequent interruptions of service...
In that case the only thing to do is to come back a bit later!

It's been fixed by Hostgator. It was a problem of permission messed up for some reason beyond my skills. Maybe uploading issues. I might think about switching for Zenphoto hosting. Tks.