The most pernicious threat to your PC's data isn't a dead hard drive, a rogue virus or a stray bolt of lightning. It's human nature. The only sure-fire way to protect your files is to back them up. And that takes time and money, two things most people don't like to spend. Here are a few ideas that can speed the task of backing up while keeping costs to a minimum.

If you have relatively few data files to back up, choosing the right storage media is easy. If you measure your files in kilobytes, they'll fit on a floppy disk. If you have megabytes of data, you'll need the storage space of a Zip or a CD-RW drive. And to handle gigabytes, choose an Iomega Jaz drive or a similar device. Of course, the more data you back up, the more it costs and the longer it takes.

Still, backing up your entire hard disk -- OS, applications, and all -- has some great advantages. With everything saved, you can easily replace a dead hard disk and immediately restore Windows and all your applications and data without tedious reinstallations. In some cases, overwriting a troublesome install of Windows with an earlier, cleaner copy can save you hours of effort spent tracking down software incompatibilities or damaged program files.

Unfortunately, backing up an entire drive requires lots of storage space. Using a 100MB Zip drive to back up gigabytes of data is inconvenient at best. Larger-capacity drives, such as CD-RW or Jaz drives, though faster, cost well over $300.

For a happy medium, consider buying a second hard drive. An 8GB drive costs between $200 and $250. And hard disks are relatively easy to install. These days, just about every CMOS program has a hard disk autodetect feature. Unlike some removable storage drives, EIDE hard drives have few Windows-related compatibility problems or driver issues. Compared to most removable storage devices, EIDE hard drives are extremely fast, making them ideal for backing up or restoring data.

There is one catch: because hard drives aren't removable, you can't store your backups off-site. As a precaution against fire or other disaster, you should keep a backup of any vital data in a different location.