A few days ago our neighborhood had a planned power outage. The power company sent out notices that they'd be disconnecting us for work on a nearby street. They blocked that street off all day, so I hope they further informed its residents that they wouldn't be able to get out of their driveways.
So, before I left for the day, I turned my computer off. When I turned it back on afterwards, the light came on, the machine emitted three beeps, but nothing else happened. Uh-oh. Good thing that I've acquired a portable hard drive, a much more useful tool, methinks, than flash drives for backups. (Flash drives are more convenient for carrying files around between computers.)
What do the three beeps mean, anyway? They must be a message of some kind, and since computers don't write their own messages, somebody programmed them, they must mean something. But neither of the phone computer help services I consulted knew anything more than "your hard drive crashed."
It turned out it hadn't. Before trying to take it in, I disconnected everything, and then thought, I'd better dust this down. So I dusted the outside, and then opened up the case and dusted and blew off (compressed air) the inside. Then I disconnected the cables to the hard drive, cleaned everything there off, and reconnected them. (Knowing these on sight is as virtuoso as my knowledge of computer hardware gets.)
Then I tried plugging the power back in, and sure enough, it worked just fine. I saved both time and money. Disaster narrowly averted.