Based on your replies I would assume you have no idea what is in your computer besides the CPU and that your GPU is Nvidia based. You are going to need to do a hardware inventory of your system and install all of the device drivers for your system.
if you go here ->
http://www.geforce.com/Drivers
and run the auto detect it should find the proper driver for your GPU so you can download and install it on your system this should fix your graphics driver issue.
Besides that I am wondering are there and yellow exclamation marks in your device manager and if so what are they? (control panel -> system -> device manager)