I try to install roundcube in windows, but I got an error below:

DB Error in F:\webmail\program\include\rcube_db.inc (63): DB Error: extension not found
Fatal error: Call to undefined method DB_Error::query() in F:\webmail\program\include\rcube_db.inc on line 124

My environment:

windows 2003

IIS 6.0

php-5.1.1

pear-1.4.5

DB-1[1].7.6

MySQL 5.0.13

php.ini
include_path=".;C:\php5\pear;c:\php5\includes"

extension_dir = "C:\php5\ext"

extension=php_mysql.dll

db.inc.php

$rcmail_config['db_dsnw'] = 'mysql://roundcube:roundcube@localhost/roundcube';
$rcmail_config['db_dsnr'] = '';

I search all archives in lists.roundcube.net, but I coudn't find a helpful answer.

Thanks to anyone response to the subject.