Do you know what to write to the page.tpl.php file so that it shows only 5 regions (header, menu, left_sidebar, content, right_sidebar)? Something like the following code, but to work correctly with other Drupal files and components (like *.info file) and don't collide with Drupal default regions.
<body>
<div id="header"><?php print $page['header']; ?></div>
<div id="menu"><?php print $page['menu']; ?></div>
<div id="left"><?php print $page['left']; ?></div>
<div id="content"><?php print $page['content']; ?></div>
<div id="right"><?php print $page['right']; ?></div>
</body>