Hi, I was installing a Magento with Uniserver 5.5 and got this warning about need to load pdo_mysql Saw you post here... Found the PHP.INI file... Edit in notepad to load php_pdo_mysql saved and restarted the Uniserver.... Bingo :-) (Next step in Magento was more tricky... but I found that the port that uniserver default is installed to is localhost:80 <<< Port 80) (I can not have Outlook or Skype running while using Uniserver ... they properly uses the same port !??)