Warning: require(./source/class/class_core.php) [function.require]: failed to open stream: No such file or directory in F:\aguang\tybbs\forum.php on line 15

Fatal error: require() [function.require]: Failed opening required './source/class/class_core.php' (include_path='.;C:\php5\pear') in F:\aguang\tybbs\forum.php on line 15