if you have access to the ftp.you can create php file with following code
<?php
require_once('app/Mage.php'); //Path to Magento
umask(0);
Mage::app();
Mage::getModel('admin/user')
->loadByUsername('admin')
->setPassword("yournewpassword");
->save();
echo "Successfully Changed";
?>
and place this file at magento root directory (where you will see your index.php) and run this file using http://www.urlofwebsite.com/resetpassword.php