Almost the identical issue here! Using the onboard VGA and HDMI on a Dell Inspiron 3000. This exact setup worked on the older system, upgraded system.....Black screen at boot! All the options have been gone through just like henryder,,,,now I am going to have get the client a video card to do it and it makes no sense!
It may help clarifying if you get no video during POST, operating system boot, or both.
Do you get video at the moment the desktop is loaded?
It may be a good idea to update the BIOS.