If your PDO scripts are crashing Apache after installing xampp 1.7 for windows all you need to do is:

• download this package http://windows.php.net/downloads/releases/php-5.2.11-nts-Win32-VC6-x86.zip"
• unzip
• copy libmysql.dll into xampp\apache\bin and xampp\php
• restart apache

All should be good now.