Fatal error in magento v 1.5

I have installed the follow up email extension in my magento V1.5.. After installed admin panel which is display like this:

Fatal error: Class 'Mage_Followupemail_Helper_Data' not found in /home/shared/nftn/app/Mage.php on line 520

$registryKey = '_helper/' . $name;
if (!self::registry($registryKey)) {
        $helperClass =开发者_高级运维 self::getConfig()->getHelperClassName($name);
        self::register($registryKey, new $helperClass);
}

I don't know how to remove that error. Can any one tell me????

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Looks like the error is caused by the Followup Email extension. If you remove all it's files, the error has to be gone.