The Asus P5LD2 has two PCI-E X16 slots while there is also an SLI bridge included in the retail package. The first slot, the blue one, is 16X in both single and dual video modes while the black can also be set to 2X, 4X or Auto. With NVidia's 7.1.8.4 and 77.77 drivers we used, we weren't be able to enable SLI for this board. Instead of this, the dual PCI-E video slots can be used for powering up four screens, in quad display.
Lastly, the dual PCI-Express x16 slots are a most unexpected feature for an Intel chipset-based motherboard. While ASUS has supplied a flexible SLI bridge connector, the official word on these two slots is that they allow the user to connect two PCIe x16 video cards to the motherboard, allowing for quad-head display. SLI will be a viable option once NVIDIA decides to release ForceWare drivers which support SLI on non-nForce 4 chipsets.