Googling the "HAL.DLL missing" delivers a wide variety of possibilities. I've never had this mishap before, and I checked with the tech guys and they said, "Sometimes it's a dual boot, sometimes it's newly-installed hardware, new drivers..."
But they didn't remember any specific solutions (other than the ubiquitous "Time for a clean re-install". You do know how to save the Activation Key files, yes?)
LinoG, I had the feeling that you might google these issues AND if you find one that fits your circumstance, perhaps start again here and we can help.
There seems to be a variety of possibilities, each requiring a host of questions back to you first, though.