Hi anplica. Welcome to the forums :)

There are a few different ways to install this thing. I usually use Fantastico to create the database, then grab the /conf/basic_config.php file so I have the connection info, then pop it into the version I want to install. There is also a way that the wikimanual talks about where you chmod /conf/basic_config.php and give it the database connection info online. Finally, one might manually create a database then either pre-edit the file or use the online method.

So! Which way are you installing this thing? Cuz basically it'll boil down to 4 or actually 7 lines in /conf/basic_config.php that need to be right for it to install. The first 4 are really critical for the database stuff.

$db_config = array(
	'user'          => 'demouser',     // your MySQL username
	'password'      => 'demopass',     // ...and password
	'name'          => 'b2evolution',  // the name of the database
	'host'          => 'localhost',    // MySQL Server (typically 'localhost')
);

Have you or can you pre-edit that file before uploading it? For my installations (including the one time where I actually made the database myself) my 'user' and 'name' are a match. 'host' is always localhost for me.

Two more lines that need to be right, but are not the connection problem you're having, are

$baseurl = 'http://localhost/b2evolution/blogs/';
// ... and ...
$admin_email = 'postmaster@localhost';

Finally, if you edit the file before uploading it make sure you change

$config_is_done = 0;

to a 1.

Hope it helps!