When I run the setup.php, I get an internal error 500 saying that there is an issue.
Most likely causes:
•The website is under maintenance.
•The website has a programming error.

I extracted the files to /public_html/portfolio/zenphoto

I set the .htaccess to /portfolio/zenphoto with no change
I deleted the .htaccess file with no change
I get the same error when I got to http://www.lynneoulman.com/portfolio/zenphoto as well.

This is my server setup - it's hosted with cpanel if that helps.

Apache version 2.2.13 (Unix)
PHP version 5.2.9
MySQL version 5.0.81-community-
log

Best guess it that there is some kind of file/folder permissions problem. There might also be a PHP error. Please review your CSG logs to see if there is anything in them that might be a clue.

I know the original post is quite old but I am also getting the error 500 on a new install. I get no error in the PHP log but I do get the apache log error:

"The process has forked and you cannot use this CoreFoundation functionality safely. You MUST exec().
Break on __THE_PROCESS_HAS_FORKED_AND_YOU_CANNOT_USE_THIS_COREFOUNDATION_FUNCTIONALITY_YOU_MUST_EXEC() to debug."

I followed the instructions on confirming permissions and all are correct.

Running MAMP on a M4 Mac mini Pro
PHP: 8.2.26
MySQL: 8.0.40
Graphics Library: ImageMagick ImageMagick 7.1.0-23

That's most likely a MAMP error. Since their upgrades from 6.9 there are different issues with each new release (7.0, 7.1. and 7.2)
I get the same specific error with MAMP 7.2 and can only hope they will fix it soon.
Meanwhile I still have to use MAMP 6.9

Thank you. I checked permissions and such but could not make it change.

As mentioned MAMP 7.* is heavily buggy. Use 6.9 instead for now as that for sure works.