A Database Error Occurred

Hi, there. I am a Chinese PHPer. I think InvoicePlane is great after I try the demo online. When I try to install InvoicePlane in localhost, I see this error message:

Unable to connect to your database server using the provided settings.
Filename: I:\phpStudy\WWW\InvoicePlane\system\database\DB_driver.php
Line Number: 125

How can I fix that?

Did you exactly followed the installation guide?