Warning: require_once(Zend/Loader.php) [function.require-once]: failed to open stream: No such file or directory in D:\xampp\htdocs\ThinkPHP\Extend\Vendor\Zend\Loader\Autoloader.php on line 24

Fatal error: require_once() [function.require]: Failed opening required 'Zend/Loader.php' (include_path='.;C:\php\pear') in D:\xampp\htdocs\ThinkPHP\Extend\Vendor\Zend\Loader\Autoloader.php on line 24