I have a compulsive personality, so I frequently back up my computer disk drives to safeguard my data in case a failure in the drive wipes out my files. Sometimes I think I don't back up my data often enough. If I go two weeks without copying an important file to a separate disk drive, I start to sweat.

I don't wonder if my disk drive will fail; I wonder when. It has happened to me, and I've known many people who have lost important files to disk failure.

To be safe in the past, I used tape or CD-R to store second and even third copies of my files. (The third copy allows you to store the two back up copies in two separate locations to guard against fire and similar problems in the original location.) More recently, as the cost of hard disks dropped low enough, I started to use external hard disk drives to store my second copy.

All these methods are good but, in general, still not good enough. They each take a lot of time, and if you don't store the additional copy in a separate location, you're still susceptible to a fire or other disaster.

David Friend and other entrepreneurs in Boston figured out that storing backup data on the Internet would be a better solution. But he realized that if he used traditional methods to offer a service to do the backups, it would still be susceptible to many of the same problems. So he created a service named Carbonite, referring to a strong material in Star Wars, that does it a bit differently.

Mr. Friend determined that more people would back up data if it were automatic, like traditional enterprise backup systems, and one-button easy. The first part was easy, but making it easy is tougher. Yet his team came up with a method that watches your PC; then backs up any changed files whenever you're connected to the Internet. You'll always know which files have been backed up by a symbol that changes color depending on whether the file has been backed up.

You don't need to make and store your stack of CDs, DVDs or tapes; and you don't have to worry about your backup drive being in the same location as your PC, because it's somewhere else. You don't even need to worry about data theft because Carbonite encrypts your files before they ever leave your PC, so they can't be viewed at the server or on the way there.

With Carbonite, you can back up as much data as your PC can hold, and today that can be hundreds of Gigabytes. So if you don't mind keeping your PC connected to the Net for long periods, you can back up all those audio files and home movies in digital format. No more worrying about whether those family memories or important one-of-a-kind documents will be there if your laptop is stolen or the PC crashes and burns. Carbonite does it in the background so it doesn't interfere with your work, and even chooses which files to give priority so it gets the most files backed up in the least amount of time.

Carbonite is available by subscription at a cost of $49 a year for each PC. For businesses that aren't yet backing up their data, that's a no-brainer purchase, and probably should be for home users too. After all, you probably spend that much on anti-virus software and spyware sniffing software. Yet drive failure is more likely and often more devastating than either of the other threats. A free trial is available at www.carbonite.com.