我在action文件夹下建立了个HelloAction.class.php，里面写了个方法index（）；进入http://localhost/MyApp/index.php/Hello/index就出现下列错误
找了好久也找不到原因，求帮助

错误位置
FILE: C:\wamp\www\ThinkPHP\Lib\Core\App.class.php 　LINE: 122
TRACE
[13-03-03 16:00:03] C:\wamp\www\ThinkPHP\Lib\Core\App.class.php (122) _404(无法加载模块:Hello)
[13-03-03 16:00:03] C:\wamp\www\ThinkPHP\Lib\Core\App.class.php (207) App::exec()
[13-03-03 16:00:03] C:\wamp\www\ThinkPHP\Lib\Core\Think.class.php (39) App::run()
[13-03-03 16:00:03] C:\wamp\www\ThinkPHP\Common\runtime.php (242) Think::start()
[13-03-03 16:00:03] C:\wamp\www\ThinkPHP\ThinkPHP.php (30) require(C:\wamp\www\ThinkPHP\Common\runtime.php)
[13-03-03 16:00:03] C:\wamp\www\MyApp\index.php (5) require(C:\wamp\www\ThinkPHP\ThinkPHP.php)
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