Connection Error

At last I managed to create a database and the install.php went also ok.
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Advanced Guestbook Tables were created successfully!

Your selected database: 100_gast
Your MySQL host: 100_gast
Your MySQL username: 100_gast

Click now here to setup the guestbook admin...

=========
== after clicking the link I get the following error
=========

Warning: mysql_connect(): Access denied for user 'root'@'localhost' (using password: NO) in /home/100/domains/100.nl/public_html/gastenboek/lib/mysql.class.php on line 30
Connection Error

MySQL Error : Connection Error
Error Number: 1045 Access denied for user 'root'@'localhost' (using password: NO)
Date : Tue, July 26, 2005 23:50:54
IP : 00.00.124.54
Browser : Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.5) Gecko/20041107 Firefox/0.10.1
Referer : http://fake.nl/guestbook/install.php
PHP Version : 4.4.0
OS : Linux
Server : Apache/1.3.33 (Unix) mod_jk/1.2.13 mod_ssl/2.8.22 OpenSSL/0.9.7a PHP/4.4.0 mod_perl/1.29 FrontPage/5.0.2.2510
Server Name : www.100.nl

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what can I do to solve this error?
I've given write permissions to -public -tmp and -admin

thanks

Your selected database: 100_gast
Your MySQL host: 100_gast
Your MySQL username: 100_gast

You need to put this info into the config.inc.php file as well.