Task
You already have a working WordPress (WP) site.  Now, you need to add one more site with a new MySQL database.  This document describes how to add one more database and install a new WP site on the same server.

Download
Download latest WordPress ZIP package (3.X) and unzip it to your future site location.
Open IIS Admin
Create a new virtual directory pointing to that location

Create a New Database
Use MYSQL Client (command shell)
You need to know your current MySQL root user password
Add a new database –
CREATE DATABASE Your_DB_Name;
Do NOT forget ; at the end of each command

Get the list of all users:
SELECT user FROM mysql.user;

Grant access to this new database:
GRANT ALL PRIVILEGES ON Your_DB_Name.* TO “YourUserName”@”localhost”;

Reload grant tables:
FLUSH PRIVILEGES;

Edit    wp-config.php
Rename wp-config-sample.php into wp-config.php
Edit wp-config.php and set these parameters:
DB_NAME
DB_USER
DB_PASSWORD

Set the table prefix for something suitable to your site:
$table_prefix  = ‘sc_’;

Cofigure Your Site
Point your browser to:
your_site/wp-admin/install.php
You might see an error:
“Error establishing a database connection”
Check D/B name, user name or password
Try again
See WELCOME screen

WP is now communicating with new MySQL database
Create and Write down your admin site user ID and password
Login with your new credentials
You are done!