I have had mixed results with onboard intel chipsets whether its not commuicating with the monitor properly or something else. But as dipankar2007ind said it would be best if you could list either the specific VGA, or motherboard. or specific Asus computer model.
If you are sure it is an intel graphics card go here:http://downloadcenter.intel.com/default.aspx?iid=gg_support-EN_01+home_downloadctr
On the top click on run the driver update utility and it will find and download/install the new drivers.