OK, first of all, I did everything wrong. I upgraded (or made the attempt) to 2.0 but I didn't follow the instructions. I just uploaded the new files to my server. Then I lost connection to everything and thought that would be a good time to read the directions. So I walked through the upgrade instructions. Each time I attempted to access install.php I got "Error establishing databasse connection." Then I just tried to install as though I was starting over. Same error message.
I manage my own server using cPanel. When I checked the database, it was still there but was not called "wordpress" but "wrdp1". I did not make that change.
My config file looks like this:
// ** MySQL settings ** //
define('DB_NAME', 'wordpress'); // The name of the database
define('DB_USER', 'firstname.lastname@example.org'); // Your MySQL username
define('DB_PASSWORD', 'xxxxx'); // ...and password
define('DB_HOST', 'www.ariadne.org'); // 99% chance you won't need to change this value
So I tried changing the db name and user to what it was on cPanel. Nothing worked. I changed so many things so many times with no results that I deleted 2.0 from the server and reinstalled 1.5. To the best of my knowledge I have put everything back just as it was before and I still get the same error message.