When laptops refuse to start-up

My sister called me today at work.

Catherine: "Nick you've got to check out my laptop. It doesn't start-up!"
Me: "What? Did you broke it?"
Catherine: "Noooooo"

It was about my old Acer Aspire 5101 ANWLMi laptop which she now owns. My sister uses it only to surf the Internet, checking out her Facebook profile, emailing, writing documents, e.t.c. Aspire 5101 is a fine machine for that stuff.

And here I am, ready to check it out.
Boot. BIOS screen. System checking. System test loops infinitely. Motherboard problem?

Ah, good bye laptop. RIP. You served us well.
That was my initial thought. Well, it lasted only 10 seconds because I had already experienced a similar problem with my new laptop, which you can view in the About page.

A different version of the same problem, to be more precise. My (new) laptop didn't display a BIOS start-up screen. Just a black screen. Plus when I tried to switch it off, it would refuse to obey me, and its heat started to rise. The only solution, of course, was to unplug the battery. OK, I did that. I waited 2-3 seconds, then I put the battery back in the laptop, turn it on, and voila. It worked!

I don't think the battery caused the laptop to malfunction (in my case) but rather the mainboard. The batteries on both laptops work fine, and the recurrence of the same problem on a different laptop testify (?) my allegation. And yes, the battery trick worked on the Acer laptop, too, thankfully.

To be honest, I wouldn't have the slightest clue if I hadn't experienced the "black screen" mystery in the past. The automatic "system testing" on the Acer laptop was misleading and I would had thrown in the towel and sent it to professional technicians to resurrect it.