Warning: require(__DIR__/thinkphp/start.php) [function.require]: failed to open stream: No such file or directory in D:\WWW\031\index.php on line 18

Fatal error: require() [function.require]: Failed opening required '__DIR__/thinkphp/start.php' (include_path='.;C:\php5\pear') in D:\WWW\031\index.php on line 18