Problem With Sapphire X800 GTO

Sounds to me like you need to disable your onboard video if you have one, if you do go into your mainboard bios and disable your onboard video, and make sure that it's also set to use AGP first.

Then you might want to make sure nothing is Over Clocked on your system, CPU, Vid Card, Memory that could be causing the lag and crashes.

and if all else fails backup your important stuff and do clean install of WinXP.

I have that same card you have great card once you get it working

BTW
Making sure you uninstall old drivers are very important, you say you have a nVidia card not sure if it's onboard or not, as that can cause some issues, uninstall all video drivers and make sure winXP uses standard VGA adpter before you install new drivers, and make sure you have Anti-Virus programs off durring install as that can cause some problems as well.

Hope this helps

Hmmmm!

If you are seeing 2 VGA adapters in device manager, the only thing I can think of is that the drivers for either card didn't get uninstalled all the way, and I believe you can't removed the second without first putting in the card that was taken out.

So uninstall both cards and drivers, pop back in the other one install it and then uninstall it, that should remove the double VGA in device manager.

if you take out old card without uninstalling it and pop in new card and install drivers for it, that is going to give you major problems.

and you might want to get a regiersty cleaner, ccleaner comes to mind and run that before you install drivers again, but make sure your system is display driver free before install.