MSSQL with php 5.3 could not find driver

Hi i keep getting the following error:

CDbConnection failed to open the DB connection: could not find driver.

I am working in the following enviroment which cannot be changed:

  • Windows server 2003 with IIS6

  • msSql 2005

  • PHP 5.3.2 VC9

And i get the following error:

CDbConnection failed to open the DB connection: could not find driver

I have read that PDO has some issues with VC9 as it has since it uses an ancient library that is no longer supported by MS. Has anybody else got this working or know of a workaround. We have a fairly high traffic site being managed with a Yii framework app that we need to upgrade from version 1.0.0.4 to 1.1.3 as part of a migration plan and part of an overall web upgrade. We really need this to work. I have been googling for two days without any success. Please help.

Any luck?