gostaria de saber o que é ese erro, sempre que eu acesso o localhost:8090/install/install.php pra instalar o forum aparece essa mensagem

Warning: require_once(C:\AppServ\www/includes/class_core.php) [function.require-once]: failed to open stream: No such file or directory in C:\AppServ\www\install\init.php on line 35

Fatal error: require_once() [function.require]: Failed opening required 'C:\AppServ\www/includes/class_core.php' (include_path='.;C:\php5\pear') in C:\AppServ\www\install\init.php on line 35