I guess that his mean what is version of bios mod (UEFI or Legacy BIOS) that you are using.
Exactly as this!!, the reason I ask which bios, is because the UEFI bios is in effect, still being tested out by those who have wanted to try it out early, i.e., before a final release / guide.
There may well be a few bugs, including some in windows that have not been experienced by others yet.
It may not be bios related at all, in which case it would be interesting to know if HDMI was tested on this laptop previous to installing OSX, has another cable, and another monitor been tested to tule out external hardware issues.
Do you have dual graphics? is one of the graphics cards disabled? Does the HDMI on this laptop run from the HD3000 or other graphics card... another thing to check.
Does HDMI work in OSX?
Provide everyone with as much info as you can, what you have done, what you have tested etc..