NET RESULTS:Last week I wrote about recycling your PC - or, if it is still in good working order and of a reasonable specification, donating it. Several people e-mailed in short order to suggest it would be a good idea to remind people getting rid of any PC that they need to be extra careful about making sure they have fully wiped the drives clean. Otherwise, private and sensitive personal information may also get "recycled and reused" in some pretty undesirable ways.

Consider what most of us keep on our computers: personal records ranging from health to financial information, passwords to various sites and accounts, personal correspondence that could be sensitive, maybe work from the office that we've taken home to complete.

Many of us use the "autofill" feature for forms, meaning anyone using the computer would get our usernames and have a password automatically completed to give access to, say, a banking site.

In other words, more than enough information is readily available to enable full-scale identity theft and worse. Left- over data on business PCs can leave a company liable not only for mismanaging personal data, but also under many of the new laws regarding corporate compliance.

Deleting files does not permanently get rid of the data in them. All it does is remove them from visibility and allow the computer to overwrite them with new data. But what generally happens is pieces of the file, and often the complete file, remain recoverable for months to years because of the way in which computers store data - in fragments.

The computer is managing the equivalent of lots of documents scattered all over the floor of an enormous office, with a folder on the floor somewhere, too. When the file gets dumped, it's as if someone throws the empty folder into the bin but all the documents remain scattered around the place.

Even when people have taken steps (they think) to wipe their drives clean, often this task has not been done adequately. For example, choosing the option to reformat a drive and selecting the "simple reformat" option on Windows will not eliminate data, it simply allows it to be written over.

Even fully reformatting the drive generally does not eliminate the information completely. Information often can still be retrieved using a good software tool - even free tools available widely online.

A few years ago two Massachusetts Institute of Technology (MIT) graduate students conducted an experiment to see what private information people were unknowingly passing along with their old hard drives.

They bought 158 used drives on eBay and found that of 129 drives that actually worked, 69 had recoverable files and 49 contained personal information, including 3,700 credit card numbers, personal medical information, and pornography.

Only 12 of the usable drives had been properly wiped clean.

Drives need to be purged to what is referred to as a "US department of defense" standard - to the point where data is unrecoverable. This standard is used by companies such as Dell in their computer recycling and refurbishment programmes and by charitable groups such as Camara (www.camara.ie), which takes in unwanted PCs and gives them new lives in African communities.

How do you get data off the drive permanently yourself? Well, there is an in-built tool in most drives created since 2001 called Secure Erase, which can overwrite every track on a hard drive. Many PC manufacturers disable this to keep people from accidentally wiping their drives.

If you are an adept computer user you might find that a free tool such as Darik's Boot and Nuke (http://dban.sourceforge. net/), which makes use of Secure Erase even when it has been disabled, will do the job.

There are also a number of commercial programmes available that will enable you to wipe your drive to this standard, such as WipeDrive, Norton SystemWorks or DriveErase Pro. There are also some easy to use free tools such as Killdisk (http://www.killdisk.com/).

With any of these programmes, be sure to go back and verify that the drive has been wiped clean before you recycle or donate your PC.

blog: www.techno-culture.com