Some motherboards have 2 slots so you can run off of 2 graphics cards, not at the same time. Say you have a high-performing nVidia card and some kind of ATI All-in-Wonder, and you want to do all that multimedia stuff instead of games. I think that's what it's for. Doesn't appear to be an SLI board, but I may be wrong.
ASUS A8N32 SLI-Deluxe, AMD Athlon X2 3800+ @ 2.8GHz, eVGA 8800GTS 320MB, 2GB Corsair XMS DDR400, 160GB WD HDD + 320GB Seagate Barracuda 7200.10, AC Freezer 64 Pro, 700W OCZ GameXStream, NZXT Zero :D
I think I've decided to leave... maybe I'll come back sometime.