I'm not quite sure why you're so taken with this computer idea. You do realize that it's part of the plot of "Hitchhiker's Guide the Galaxy"?

I've got to disagree that it's part of Hitchhiker's, the idea in Hitchhiker's, as I recall, is that people are all part of a computer, a massive computer that is Earth, etc. etc.

But the people on Earth are still real: as evidenced when our hero leaves the planet and is taken elsewhere.

The idea here is that everything is part of a simulation inside a computer in what we would, subjectively, call the future. We're not parts of the computer, as in Hitchhiker's, but rather it's object. Rather than theorizing about the way their ancestors lived, as we do, constructing mental models, people in the future could create realistic models of entire universes. Within ten years, should quantum computing continue apace, we'll have the capacity to store in a single computer more information that exists in the entire universe. The position, speed, spin and charge and so on of every molecule that exists and the laws that govern them. And so, I'd imagine soon after, we'll have the ability to store more information /than there ever had been in the universe/.

The use for this?

Make more universes.