In Person of Interest, we know that the Machine is created by Harold. The power only comes to the machine by getting data from feeds, otherwise, the logic/structure was provided by Harold.
So why are they so desperate to save the Machine in the end of Season 4? In fact, team Machine is worried about the Machine in Season 3 and 4, as Samaritan came online and started searching for the Machine.
But why can't Harold make a new machine?