PHP info can't find MySql with IIS web server

I'm trying to install the latest version of PHP on a 2003 server running 
IIS.  PHP runs fine but when I run phpinfo(), it doesn't find MySql.  At the 
end of my php.ini file I have:

[PHP_MYSQL]
extension=php_mysql.dll

And

extension_dir = "c:\progra~1\PHP\ext"

In my path variable I have: 
c:\progra~1\PHP;c:\progra~1\PHP\ext;c:\progra~1\MYSQLS~1.1\bin;

Can anyone tell me what else I need to do to get PHP to recognize MySql?

Many thanks,

Steve