What thoughts about Duncan does Macbeth have that conflict with his ''black and deep desires?

Macbeth, before the murder, can never fully reconcile his desire for the throne--which is strongly encouraged on, if not coerced, by his ambitious wife--and the murder of an old man, a man who has been supportive and generous towards Macbeth, who has never used or abused Macbeth in any way. Macbeth daydreams of being king, but is afraid of the steps towards it--a brutal murder, falsely accusing the retainers in the king's death, the possibility that he will no be believed by his peers. Regicide is a crime, but it is made more terrible when the man killed was a good and just mentor undeserving of the act.