Suppose you had an identical twin with identical genes and, until very recently, an identical history. From the perspective of anyone else, you’re similar enough to be interchangeable with each other. But from your perspective, the twin would be a different person.
The brain is you, full stop. It isn’t running a computer program; its hardware and software are inseparable and developed together over the course of your life. In other words, the hardware/software distinction doesn’t apply to brains.
The ancients considered everything to be the work of spirits. The medievals considered the cosmos to be a kingdom. Early moderns likened the universe to a machine. Every age has its dominant metaphors. All of them are oversimplifications of a more complex truth.