IT seems like you do not have PDO installed in you PHP. what version of PHP you are running? it must be php5.
as a quick workaround you can edit setup.php file like below, comment out PDO cehck and set it to false.:
echo ‘pdo echeck;’;
foreach(@PDO::getAvailableDrivers() as $driver)
$use_pdo = true;
echo ‘pdo end;’;*/
$use_pdo = false; // you don’t have PDO according to your error
This will work only if you have PHP5 with no PDO. PDO is enabled by default in php 5.1 as far as I know.