Drupal7 : Error in install drupal in localhost When install drupal 7 in my localhost its show this error:-

http://im36.gulfup.com/QFe3q.png



why its not show me database type [ MySql ] 

when install in my site and install good and return install to localhost show my this error

 Fatal error: Undefined class constant 'MYSQL_ATTR_USE_BUFFERED_QUERY' in D:\AppServ\www\drupal\includes\database\mysql\database.inc on line 46
You need the php's PDO and mysql extensions installed on your system in order for Drupal to use MySql data storage. One or both of them are apparently missing, and Drupal defaults to Sqlite, which is a simple database system and only needs a writable file to work. Please refer to Drupal's system requirements page for further info.