A number of readers have asked what the difference is between "System Restore" and "System Recovery." The former is a Windows tool that lets you return your system settings to an earlier date, in case of a problem that can't be fixed by other means. Go to Start>All Programs>Accessories>System Tools>System Restore and follow the prompts.

"System Recovery" is a means of restoring a Windows-based computer to its original state in case of a non-repairable virus or a hard drive crash. All new computers come with one or more System Recovery CDs that can be used to re-install Windows and other programs that came with your PC.

Speaking of HD crashes, they can occur at any time without warning, and are the main reason you should have an ongoing backup system in place to protect your important files. One approach is to copy the files to an external drive so they can be copied back on to a restored main HD or onto a new computer. Copying data to an external HD can be done manually on a piece meal basis, or you can buy an external HD that comes with software that backs up your files automatically on a regular schedule. "Retrospect" comes with Maxtor external HDs for this purpose.

Another approach is to create a "mirror image" of your PC's hard drive with a program such as Norton "Ghost" or Acronis "True Image." These programs create an exact copy of your existing hard drive, complete with its Windows operating system, other programs you may have installed, and all your personal data files. This kind of thorough backup can be critical for a business whose day-to-day operations depend on a fail-proof computer system.

Personally, I have no such critical needs in my computer work — so I just backup my files at random intervals, knowing I can always restore Windows and other programs from their original sources. Furthermore, most of what I create goes on this site, which then becomes an auxiliary backup resource.

A web-based email service, such as Gmail or Hotmail, can also be an excellent backup resource for any files that can be attached to an email message. In fact, Google's Gmail advertises that "you will never have to delete another message" because of the huge storage space they offer a user. I routinely email text documents (like this column) to myself via Gmail, knowing they will always be available from any computer with an Internet connection, as well as being available in case my personal computer crashes or is lost or stolen.

Speaking of text docs, I've written in the past about how I keep a print-out of my medical history at home and in my car in case of an emergency. Well, what if I'm not at home or in my car when something happens? Now I also keep a copy of the med doc on a USB flash drive attached to my key ring.