I have a Dell Dimension 3000. The video ‘card’ is integrated. In 'System Info (control panel) they call it an “Intel 82865G Graphics Controller”. Is there any way to add a video card, e.g., NVidia, and if I do, do I have to somehow disable the Graphics Controller?
To directly answer your post, no you don’t have to add or disable anything. It will just switch to using your new card.
You should just be able to install a new video card, no problem - no extra configurations necessary.
After a quick google search, it seems that the 3000s have no AGP or PCIe slot. There’s only PCI slots for expansion. This means you’re extremely limited with the choice and performance of graphic cards that you can add. You better open up the box and take a look inside to confirm this, because this really sucks for you.
There’s not many current cards out there still available in PCI. Take a look here. The Nvidia Geforce FX 5500/5200 is probably the best choice here.
I guess one up-side is that you know you won’t have to spend more than $100.
addendum:
It seems that BFG used to make a Geforce 6200 available in PCI, and this is the the most powerful PCI card for Blender.
If you add a new graphics card, I think it would be best to disable your current onboard graphics card in the bios. Onboard graphics cards use your system RAM (IIRC), so if you add a new graphics card, and your onboard one does not automatically disable itself, or you disable it from the bios, your system won’t run at peak performance, due to the fact that your old graphics card would still be running and using your PC’s RAM. I could be wrong, though, so if I am, just disregard what I said.