dual computer monitors

need some help!
windows xp

I had to unplug the kids computer. when I went back to hook it all up again, it is running in dual monitor mode.
It has a "stock" video card that came in the Insignia computer and a GForce card that I added. I only want the GForce one to work. It has been a while since I configured it the first time and cant remember what I had to do.
The desk top is on 1 monitor, and everything that you open appears on the other monitor

I just need it to run one 1!! help!!!!

You should be able to disable the onboard VGA in the bios.

Right click on the desktop, go to properties, then settings and select which monitor you don't want to run (2), then uncheck extend to this monitor. That's what works for me.