Whats interesting with PCIe is the massive compatibility. Any PCIe device will work in any PCIe slot. A modern PCIe 2.1 x16 video card will work in a PCIe 1.0 x1 slot.
The video card won't even fit into the x1 slot, but if you file a notch into the card, or file down the back of the plastic on the slot to make it fit, it will work.