Backup drives: essential but underused.(COMPUTER SECURITY)(Buyers guide)

Home computers hold a lot we care about, from pictures to music to letters. Yet most of us are surprisingly cavalier about copying that often-irreplaceable material to another location for safekeeping. One recent survey found that fewer than half of us ever do so.

With the cost of storage dropping, there's really no excuse not to back up your computer. For most people, the best backup location is a computer peripheral known as an external hard drive. High in capacity and convenience, this device allows you to easily back up new content immediately. As our Ratings show, these days a worthy hard drive can cost as little as $200 or so and need take up no more space than a typical hardback book.

Setting up an external drive does require a half-hour or so and moderate technical know-how. (However, it's easier than installing a second hard drive in your computer, another backup option.) After that, backing up to an external drive typically demands only a few keystrokes and a minute or two just before you shut down the computer. You can keep working on other tasks during the process. Or you can have the drive back up automatically at a preset daily time or times.

The 10 drives we tested varied in ease of use, most due to the design of their included software and the presence (or absence) of certain features, as detailed in the Ratings on the facing page. There was little relationship between price and performance within the group.

HOW TO CHOOSE

Buy a 250- to 300-gigabyte drive. Such capacity should accommodate your needs well into the future. You'll save relatively little by buying less capacity; for example, a 160-GB drive (the smallest common size) may save you only $60 or so. Be aware that 250- to 300-GB drives that cost significantly less than those we tested may lack software (an extra $30-and-up expense) and be light on features.

If you have several computers, consider a networkable drive. This kind can be partitioned and plugged into a home network, where it can receive data from computers throughout the home. Be aware that installation is more difficult with wireless (Wi-Fi) networks than with wired ones, and backup is about 10 times slower than with wired connections. However, if your …