6600 @ 2.4 I'm assuming is a E6600 which is a dual core not single in which case thats fine for gaming and more than enough for CSS. Try doing a complete uninstall of your current video drivers and then boot up in safe mode and run a program called Driver Sweeper to get rid of any left over files, reboot, then install the latest drivers that you can get directly off of Nvidia's web site. If that that doesn't fix it then there may be something else wrong.