Go here (http://belarc.com/free_download.html) and download Belarc Advisor. Run it, and it will give you a good list of everything in your computer...including your graphics card.
sometimes if you search in google you can find a registry value for nvidia that will allow you to overclock your videocard from the nvidia display when right clicking on the desktop. I know one exists for a geforce 5600...
for overclocking video cards, use Rivatuner
it's designed for Nvidia, but apparently works with ATI cards too (although I haven't tried it with an ATI card)