problem with PDO ODBC on Win2k3 server

I'm having a problem whereby PHP can't seem to load the php_pdo_odbc.dll extension. The server has PHP 5.2.8 installed to "C:\Program Files\PHP" and in the "C:\Program Files\PHP\ext" folder I have php_pdo.dll and php_pdo_odbc.dll. At the bottom of the only php.ini file on the server are the following lines: [PHP_PDO] extension=php_pdo.dll [PHP_PDO_ODBC] extension=php_pdo_odbc.dll The extension directory is set to the following: extension_dir ="C:\Program Files\PHP\ext" The system event viewer logs the following event: Application popup: Warning : PHP Startup: Unable to load dynamic library 'C:\Program Files\PHP\ext\php_pdo_odbc.dll' - The specified module could not be found. I have checked that the file is actually there, and I've also tried adding a trailing slash to the extension_dir directive and restarting IIS to see if that helped. It still can't load the ODBC module. any ideas?