Expect the best, prepare for the worst, according to the maxim. This plays out in interesting ways with personal computers.

Computer disasters run the gamut, resulting from such causes as computer viruses, hard disk crashes, accidentally erased files, accidentally reformatted disks, sabotage, theft, lightning strikes, fires, floods, hurricanes, tornadoes, earthquakes, and even terrorist bombings.

The recent trio on the East Coast of rare earthquake, rare tornadoes, and common enough hurricane emphasizes the reality of natural disasters.

A ruined computer or broken hard drive may not be anywhere near as tragic as the loss of life, but computer disasters can and have cost people lots of money and hassle, and when crucial data was irretrievably lost, they've even caused some businesses to fail.

An ounce of prevention is worth a pound of cure, according to another relevant maxim.

Here are some important, and relatively easy, preventive measures that any computer user, whether in a business, professional, or home setting, can take.

Back up your data. This has always been and remains the single most important disaster prevention measure. Even if your computer or other device gets trashed, as long as your data is intact, you're good to go on a new device.

USB flash drives, also called flash drives or thumb drives, let you store lots of data on a device you can pop into your pocket when heading for safe ground. Kingston Technology (www.kingston.com) offers its brand of DataTraveler flash drives with capacities from 2 to 256 gigabytes targeted to consumers, businesses, and government agencies.

Though backing up through a "cloud" service over the Internet takes more time, it's safer since the data is already off site. Some are free, some cost.

BackBlaze (www.backblaze.com) charges $5 per month or $50 per year to back up unlimited data from one computer. Amazon Cloud Drive (https://www.amazon.com/clouddrive/learnmore/ref=sa_menu_acd_lrn2) lets you upload as much as 5 gigabytes of data for free, with charges for additional data.

Keep the electricity flowing. When you lose power, an uninterruptible power supply (UPS) provides enough electricity to let you save documents you're working on and power down properly to avoid problems or, depending on the type, to keep on working. APC (www.apc.com) offers UPSs for a wide variety of users, from those working in home settings to data centers.

For portable devices, a battery pack can charge laptops, netbooks, tablets, and smartphones when the power is out. XPal Power (www.xpalpower.com) offers a range of power packs, from the XP600, which you can carry in your wallet or purse to charge a cell phone, to the XP1800, which can charge three portable devices at the same time.

Consider worst-case scenarios. When you don't have backups or the backups are faulty, all's not necessarily lost. If you're a do-it-yourselfer, software programs can sometimes recover trashed data, a less expensive option. If you're not technically oriented or if the problem is beyond your technical expertise, companies can do the work for you, a considerably more expensive but more reliable option.

R-Tools Technology (www.r-tt.com) offers a range of programs for Windows PCs, Macs, and Linux computers. Its R-Studio program, which costs $79.99, handles different kinds of hard drives and different operating systems.

Seagate Recovery Services (http://services.seagate.com/?SR=sr3_183804895_), part of hard drive manufacturer Seagate Technology, can recover data off trashed hard drives from any manufacturer. In existence since 1989, it works with businesses and consumers, offering priority as well as economy service. If it can't recover your data, it refunds your recovery fee.

Seagate offers good advice on what to do and what not to do when you realize you've lost data, which is similar to the advice offered by other data recovery services.

If your hard drive is making unusual noises, you should shut it down immediately and not power up again. Even just running programs can write new data over data you don't want to lose.

If you can't access your hard drive, first eliminate the simplest possible causes, such as loose cables. As long as the hard drive isn't making unusual noises, sometimes simply restarting the computer can fix the problem.

Like other data recovery services, Seagate recommends that you don't use do-it-yourself data recovery software, which it says can make it more difficult for it to recover data and possibly cause further data loss.

Better than having to make the decision of inexpensive data recovery software or expensive date recovery service is to avoid having to use either. Back up crucial data, and make sure the backups are good.