The AGP slot may only accept either 1.5V or 3.3V cards. Select below what looks more closely to your slot.
AGP 2x/1x slot: (AGP 1.0, 3.3V)
AGP 8x/4x-only slot: (AGP 3.0, 0.8V/1.5V)
Note that they are both keyed in different locations.
An AGP 2x/1x card is not compatible with a 1.5V-only slot (AGP 8x/4x-only) and vice versa.