You can do this easy like this in the following steps.
1. In ADMIN => GLOBAL OPTIONS change all the paths and urls to be reviews not reviewpost and hit save. Do not worry the application will break now.
2. Edit the config-inc.php file via ftp and change the server path in that file to be reviews not reviewpost save the changes
3. Rename the directory on your server to be reviews not reviewpost
There you go it will not work under reviews