Do you have the original CD's that came with the Computer? There should be one that has the operating system and one that has the drivers on it. If you have not installed the drivers for the video did you install the other drivers? If so where did you get those ones from such as the Ethernet drivers and sound card drivers?
CLICK HERE for driver support for gateway. All you have to do is enter your serial number on your computer and it should bring up a list of the drivers you need for your particular computer....