Your computer is not invulnerable. Hard-drive failures happen, as do floods, fires, earthquakes, thefts, and other calamities. The hardware in your computer is replaceable, but the data inside—whether critical business documents or precious family photos—might not be. If you don’t want to face the gut-wrenching realization that you’ve lost something important, you need to have a backup plan. Here’s how you can protect yourself, right now.