There are no Windows 8 drivers for that ATI card. You need to go to the Toshiba website and see what drivers they offer there. Laptop video chipsets are often customized and the general purpose drivers for the same card model in a desktop often do not work.
If you find nothing on the Toshiba website, go to the site below and, in the automatically detect and install section, download the software -- then run it. IT will look at your chipset and tell you what is the latest driver version that will work.