Even if your motherboard only supported AGP 2.0 it will still run an NVIDIA AGP 3.0 card.
AGP 2.0 is a 1.5V AGP slot capable of 4x, 2x and 1x speeds.
AGP 3.0 is keyed like a 1.5V AGP 2.0 slot, but it only uses 0.8V of power. It supports 8x, 4x, 2x and 1x.
The connectors on AGP video cards are keyed in such a way that you can only install equipment that have compatible voltage keyed connectors.
AGP 3.0 devices can tolerate 1.5V.
From what NVIDIA says their cards are universal AGP 3.0 which can run on either 1.5V or 0.8V.
Of course nothing is perfect and if you can afford a new motherboard then it might solve your problem.
And software problems (via drivers and patches required) can cause problems just like were shown from the JPEGS.