Database Install - New Installation

[hollymax]

Hello.
I'm trying to setup the Bug Tracker 1.2.x software on a Server with Windows 2008 R2 & SQL Express 2010.
I'm to the stage of running the install.php page.
It shows the 1st eight in the list as Good, and the last for 'Attempting to connect to database as admin' as bad.
The Server name is Server2008 and the SQL Instance is SQLExpress64

I’ve tried combinations of localhost, Server2008 & SQLExpress64, however I'm assuming by the error it can't find the database.

Error shown
“Attempting to connect to database as admin BAD
Does administrative user have access to the database? ( php_network_getaddresses: getaddrinfo failed: No such host is known. )”

I've tried creating the database (without tables) manually with the user name suggested and the correct rights to it.
I have tested access to the Database with a Microsoft Data Link (.udl) and it can find the database fine with serveral different users.

config_inc.php

# --- Database Configuration ---
$g_hostname = 'localhost\SQLExpress64';
$g_db_username = 'mantisdbuser';
$g_db_password = 'mantisPassword';
$g_database_name = 'bugtracker';
$g_db_type = 'mysql';

can anyone explain what the host name needs to be please?
I do coding in html & aspx and we have a database web site in aspx running on this server.

Robert