Warning: require_once(mainfile.php) [function.require-once]: failed to open stream: No such file or directory in D:\AppServ\www\chumphonnfe\index.php on line 3

Fatal error: require_once() [function.require]: Failed opening required 'mainfile.php' (include_path='.;C:\php5\pear') in D:\AppServ\www\chumphonnfe\index.php on line 3