Ok, First, in your XF86Config file remove the following:-
Remove all of it. Then in the (Section "device") add the following:-
Option "NvAGP" "1"
Option "RenderAccel" "True"
And possibly to help the Video performance you can add the following line to your /etc/modules.conf file
options nvidia NVreg_EnableAGPSBA=1 NVreg_EnableAGPFW=1
Then restart X to make these changes active. If you booted into command mode (init 3) you can simply exit X. then type rmmod nvidia, to remove the nvidia module. Then restart X, which will reload it with the new settings. If you boot into Graphics Mode, simply reboot the system.