Not getting Signal, Turn of Secure Boot!
In Windows 8 Secure boot is enabled by default on verified Windows 8 Computers. If you install a Graphics card that is not compatible with UEFI the system will not boot. If we want to be able to use the Graphic card we must disable Secure Boot.
Power of the computer and take out the Graphics card. Then reconnect the monitor through the old Graphics card or use the onboard Graphics if present.
Now boot your system and go into your BIOS setup. For most computers this will be a key like F2. Head over to the Boot menu. (On your computer this might be on an different location the image below is from an Dell Computer.)
Now Disable Secure boot and enable Legacy Boot. This time if you insert your Graphics Card you should be able to boot up your computer.