Hi, we use these sort of phrases when we wish to express what is called Onomatopaeia, which is a big word for "sounds" of things. a low and continuous sound, pleasing to the ear, is a hum. You can make this sound by placing you lips together and attempt to say "MMMMM" - that is a hum. It also indicates that the motor, engine or mechanical device, sounds regular and correct. No screetching! good luck, Skype me for lessons if you choose. Theresa

That's exactly how I would understand it if I heard the phrase "hum to life" applied to a computer. It isn't really an idiom though. But it's a very descriptive way to describe what happens when you turn on a computer. I like it. : )

It just means the laptop hummed as it turned on (came to life). It's not an idiom or saying, the author was just being expressive.