First, I would reinstall the existing driver to make sure it isn't corrupted.

Control panel>hardware and sound>device manager... open device manager and double click display adapters then right click the graphics card info that will appear below it and select "uninstall driver".

Then reboot and the driver will automatically be reinstalled.

If that doesn't solve the problem then follow the same procedure but this time select "update driver software" and windows will try to find a newer version if available.

Try these two things and if they don't help let us know and we'll move to other things.