Let's try reinstalling your Video.
I still don't know what Operating system you are using. Win 98 98Se or Win95?
How did you reinstall? With a regular Windows install disk and other disks for your video etc? Or did you use a restore disk provided by Gateway?
This is all important information. Before I can advise you, I need to know this.
First Step. Remove the software for your Video Card.
Boot to Safe Mode. Go into Device Manager. Scroll to Display Adapters. Click on the + in front of it. Your Video will be listed there. Hightlight it and click on the Remove Button at the bottom of the page. If there is more than one instance of the adapter, remove the others too.
Go to Start>Run and choose to restart. Windows will recognize the video adapter and try to reinstall it.
This is where I need to know whether you have a CD to install these drivers. If you do, you'll need to have it ready for windows to use it as a source.
To boot to Safe Mode, reboot and for Win95, tap F8 until you see the boot menu. Choose Safe Mode.
For Windows98, boot and press CTRL until you see the boot menu.