Updating your video drivers would be the first thing to try, if you're not
sure of the hardware in your machine check out http://windows.dasmirnov.net/guides/hardware.php you'll need the video card
manufacturer and model in order to work out what drivers you need.
Once you've got that check out their respective websites and check out the
support section or download section for 'drivers'. www.ati.com and www.nvidia.com are common ones.