Delphi XE-5的help用不了

Delphi的help没法用，一点就弹出下边的对话框：
The Miscrosoft Document Explorer is not installed and the help system will not
function.Please re-install our document.

请问大家该怎么解决啊

http://jingyan.baidu.com/album/0bc808fc62a2cb1bd585b962.html