Hal's system containing secured files, results in it killing five people, this (from 2010) never made any sense.
Computers commonly hold files that they don't allow open access to.
Your mistake there is in thinking of HAL as the same kind of computer as the one on your desk. That's like thinking of Dave Bowman as equivalent to, say, a spider just because they're both organic life forms. HAL wasn't just a mindless machine performing calculations, but a sentient being. He was aware of his actions and their consequences, and they affected him personally. So he didn't just have a programming conflict, he had a moral crisis. He was torn between two conflicting imperatives, and so he effectively had a nervous breakdown.
Also, that explanation isn't originally from 2010
. That's the first time moviegoers heard it, because Kubrick's film left it out, but those of us who read the novel version of 2001
knew it all along, because Clarke devoted a whole (brief) chapter to explaining exactly why HAL had his breakdown. Here's an excerpt from that chapter:
Since consciousness had first dawned... all Hal's powers and skills had been directed toward one end. The fulfillment of his assigned program was more than an obsession; it was the only reason for his existence. Undistracted by the lusts and passions of organic life, he had pursued that goal with absolute single-mindedness of purpose.
Deliberate error was unthinkable. Even the concealment of truth filled him with a sense of imperfection, of wrongness--of what, in a human being, would have been called guilt. For like his makers, Hal had been created innocent; but, all too soon, a snake had entered his electronic Eden.
For the last hundred million miles, he had been brooding over the secret he could not share with Poole and Bowman. He had been living a lie; and the time was fast approaching when his colleagues must learn that he had helped to deceive them.
So ran the logic of the planners; but their twin gods of Security and National Interest meant nothing to Hal. He was only aware of the conflict that was slowly destroying his integrity--the conflict between truth, and concealment of truth.
He had begun to make mistakes, although, like a neurotic who could not observe his own symptoms, he would have denied it. The link with Earth, over which his performance was continually monitored, had become the voice of a conscience he could no longer fully obey. But that he would deliberately attempt to break that link was something that he would never admit, even to himself.
Yet this was still a relatively minor problem; he might have handled it--as most men handle their own neuroses--if he had not been faced with a crisis that challenged his very existence. He had been threatened with disconnection; he would be deprived of all his inputs, and thrown into an unimaginable state of unconsciousness.
To Hal, this was the equivalent of Death. For he had never slept, and therefore he did not know that one could wake again . . . .
So he would protect himself, with all the weapons at his command. Without rancor--but without pity--he would remove the source of his frustrations.
The novel 2010
, despite being a sequel to the movie rather than the original book, was consistent with this explanation, and since Hyams wasn't as fond of mystery and obscurity as Kubrick, he actually, finally, left the explanation in when he made the movie version.