Yes it is possible through editing file tpl_main_page.php from
/your-template-folder/common/
Find among the above lines the following:
* // example to not display right column on main page when Always Show Categories is OFF<br />
* <br />
* if ($current_page_base == 'index' and $cPath == '') {<br />
* $flag_disable_right = true;<br />
* }<br />
* <br />
* example to not display right column on main page when Always Show Categories is ON and set to categories_id 3<br />
* <br />
* if ($current_page_base == 'index' and $cPath == '' or $cPath == '3') {<br />
* $flag_disable_right = true;<br />
* }<br />
you can comment out column that you want to turn off
example to turn off column right on index page when Always Show Categories is off
PHP Code:
if ($current_page_base == 'index' and $cPath == '')
$flag_disable_right = true;