Step 1 Open up Control Panel and find "Device Manager"; Open it.
Step 2 Find a section called "Display Drivers" and expand the list, this should show your video card. (http://img834.imageshack.us/img834/2176/peav.png) (http://imageshack.us/photo/my-images/834/peav.png/)
Step 3 Right click your graphics card and select "Update Driver Software" At the next dialogue box select "Search for my drivers automatically" Windows should know automatically download and install the drivers ;D
If something doesn't work tell me asap.