Does your Motherboard have a built in Graphics card? if it does then take your 560 out and try starting it, if it works then you have a dead Graphics card, or inactive PCI-E slot. If it doesn't, then it could be anything form bad drivers to fried chips to fried mobo all round. I had a 9600GT that wouldn't work with the drivers installed, sometimes it bluescreened, sometimes it just didn't show anything (your problem). It turned out it's PCI-E power connector was fried and it didn't have enough power. You could be dealing with quite a simple fix if it's only drivers though.