Turn the AGP back up to 8x. That isnt going to solve anything with a CTD. You turned off fast writes, try turning off sideband addressing? Turn both AA and AF to Application Pref. Turn Vsync to Application Pref. Image settings to High Perf. Force Mipmaps none. Texture clamp off, extension limit off, trilinear optimization on, and anisotropic optimization on.
Under More Direct3D, make sure pages to render ahead is set to 1.
If you are overclocking the card, reset to normal. Make sure the fan is set to be on always. Make sure the warning for high temp is enabled.
You can turn off the sideband addressing and fast writes under AGP settings. You can also set your card back up to 8x.
Make sure the resolution you have set for your monitor is not beyond its capabilities. Try setting the refresh rate back down to 60 and see if the CTD goes away. Then you can bring it back up and see if the problem comes back. It shouldnt, but I've seen stranger things.
You didnt say what type of sound card you are using, but try turning down the hardware acceleration in your Direct X Diagnostic utility. See if that helps. Sound can cause CTD's alot, especially if you are using onboard sound.
Do you have a utility to keep track of temps inside your case and at your CPU? If not, try this utility here:
http://mbm.livewiredev.com/Check your fans, heatsinks, etc. for dust buildup. Make sure nothing is running too hot. Try taking memory out one stick at a time and see if you have some bad memory in there.
