Is this installed on your local machine? I noticed the "c" path?

Normally you don't add your own paths yourself, but XOOPS install finds the paths itself and writes to mainfile.php in the root of Xoops.

my paths look like this in mainfile.php

if ( !defined("XOOPS_MAINFILE_INCLUDED") ) {
define("XOOPS_MAINFILE_INCLUDED",1);

// XOOPS Physical Path
// Physical path to your main XOOPS directory WITHOUT trailing slash
define('XOOPS_ROOT_PATH', 'c:/apache/htdocs/xoops');

// XOOPS Virtual Path (URL)
// Virtual path to your main XOOPS directory WITHOUT trailing slash
define('XOOPS_URL', 'http://localhost/xoops');


I notice yours has the colon missing in your example ie

c: