I had an old pci-e 16x card laying around (ati radeon x1800 xl 256megs... ) I bought a pci-e 1x to 16x adapter, and a sata power to 6-pin power adapter... plugged it in and it worked. There is no way to turn off the on-board card that I can tell, but it switches to the new card... here's the wierd part... I figured if the 1x to 16 x is working, why not try using the 8x, so I also bought a 8x pci-e to 16x pci-e adapter... tried to plug that in to the pci-e 8x slot... no go. Just a black screen. Not sure why that didn't work.btw, I also modified the es1000 ati driver to use catalyst... (before trying another card)... I don't think this is necessary if you're going to use another card, and it showed only minimal performance boost. The pci-e 16x card running through 1x is good enough to play 1080p videos and that's all I needed really. I'm using this machine as a living room media computer.