Now that you've gotten yourself a new computer you're considering giving away your old one. Perhaps you have a relative, or a favorite charity, or even just a recycling/donation station that will take your old computer.

There's one thing you must do before giving it away.

Securely erase the hard drive.

It seems every day we hear of computers that have been discarded or donated by banks, hospitals, or others that later turn up only to find out that all sorts of private information that should have been erased first wasn't, and is now in the wrong hands.

It happens all the time, and it's one of the easiest ways to become the victim of identity theft.

What to do is easy: erase the data. How to do it depends on how paranoid you are.

Reformatting your disk is typically considered the right thing to do, and if done properly it's all that most need.

The catch, of course, is that word "properly".

There are two problems.

First, Windows will not actually let you format the drive that's currently running Windows. That's the most common scenario: you have one hard drive and when you start your computer it boots from that drive. In order to reformat it you need to boot from something else. It's too easy to give up at this stage and just hope that erasing files within Windows is enough. Hint: it's not.

Second: the most common kind of format, a "quick format" actually does very little except create an empty root directory on the hard disk and possibly add a label. The rest of the disk isn't touched, and more importantly isn't erased. That's why it's quick. It looks like it's erased, but in a very important way it's not and your data could potentially be recovered.

That's where disk-wiping tools come in.

There are several, and a good, free example is DBAN. Short for Darik's Boot And Nuke, DBAN is available at www.dban.org. It's purpose is simple: after downloading and burning it to a CD, you can boot from it. Once booted, DBAN will completely erase your hard drive, as securely as you like.

It's as simple as that.

There's a frequent recommendation to use a large magnet to erase a hard disk. Forget it. Hard disks are typically encased in shielding enclosures, and any magnets you might have around the house, even the really big ones, aren't likely to have any effect on the data stored on your hard disk.

For the truly paranoid, there's one more option: physical destruction.

Depending on the options chosen and techniques used it's sometimes possible to recover data from an erased hard drive. It's not simple, it's not cheap, it doesn't always work, and it's not something your average hacker can even attempt, but there are data recovery labs that can examine a hard drive in ways that might possibly recover data that had been previously erased.

If you're truly serious, physically destroying the disk platters inside the drive is guaranteed destruction.

Which of course renders your "gift" much less valuable.

For individuals, and even for banks and hospitals, the simpler and more practical approach is to use disk wiping tools like DBAN to overwrite the data securely, and then give away the computer with confidence that you're not including all your personal information as an added bonus.

Just realize that doing nothing, or just "deleting files", is risking complete data exposure.