So you only have no display, that's significantly better than it not powering on. Try your motherboards hdmi port to see if you get display. If so, it will most likely be an issue with your graphics cards, try one at a time to see if they output display individually, and then retry with your SLI bridge. It may be an issue with your drivers but I don't see that being the cause. If you have a post card on your motherboard (led number thing) tell me the post code and motherboard model. I'm not sure if your PC posted correctly as there isn't a speaker on your motherboard. I would check your power supply as well, it might be dying and not supplying enough power to your sexy SLI. Let me know the results, if your motherboard outputs display, then boot your PC and remove all drivers for your card and reinstall them, make sure they come up correctly without errors in "Device Manager".