Fatal error: Class 'PDO' not found in C:\mywebsites\drupal7\includes\database\database.inc on line 178

This is a solution from #1036110: Fatal error: Class 'PDO' not found in /home/liveaq5/public_html/juwsc/includes/database/database.inc on line 185

I had exactly this problem with a client using shared hosting.
In D6 you could just put your settings like "memory_limit=128M" in your php.ini and put the php.ini file in the web root, i.e. the same directory that index.php lives in.
In D7 it seems you need to put these 2 lines in front of it:

--------------------------- php.ini ---------------------
extension="pdo.so"
extension="pdo_mysql.so"

memory_limit=128M
---------------------------------------------------------

Really these 2 top lines should be part of the standard D7 core distribution standard settings don't we think?

Rik