Database connection with my sql

i m getting an error like this

Fatal error: Call to undefined function mysql_connect() in ..........\leftpanel.PHP on line 3


i m using mysql-version-5.0.45-win32 and php version is PHP Version 5.2.6
and sql yog version is 4.01

here is the code snippt

Code:

---

<?
$dbh=mysql_connect ('localhost','root','root');
mysql_select_db ("class");

$result=mysql_query("select * from `class`.`maincategory` order by

maincatname");
$EOF=mysql_num_rows($result);

if($EOF > 0)
{
?>

---

by googling one the net i find that uncommenting the line extension=php_mysql.dll will solve the problem but unfortunately the i m still getting an error :(

you need libmysql.dll to be in c:\windows\system32\. this file can be found in the directory PHP is installed to.

i have already copied file ,and also add php_mysql.dll in system 32 folder ,but problem is still there