Charitable move can bring on a bout of paranoia

PUBLISHED : Monday, 12 May, 2003, 12:00am
UPDATED : Monday, 12 May, 2003, 12:00am

I would like to donate my old computer to charity. However, I am very concerned that all my personal information contained in its hard disk is first permanently and irretrievably deleted.

I believe that I have formatted the hard disk (by using the command 'format c:') and want your advice on whether this is sufficient or whether, as I have recently read, it is best to 'overwrite' data with a special program.

Name and address supplied

Security is a question of paranoia: what are you prepared to do to be 'certain' about your own security paranoia? Under normal circumstances, deleting every file or reformatting the hard disk should be enough. In reality, of course, it is not.

There is rather a lot of software out there that can help you recover a trashed disk. A trashed disk is not unlike one that has been reformatted. The formatting software does not overwrite every byte of every sector of the disk, it merely puts what could be called 'markers' on the disk so that the operating system knows where the sectors are to organise all the files and directories in them.

When software attempts to recover a crashed disk, it will analyse the sectors looking for patterns. It may also attempt to recreate the directories.

Modern operating systems make things even easier because many of them keep a backup of the main directory so that it can be restored if it becomes corrupted. All of this makes it easier to recover your disk if you have lost data, but it also makes it possible for others to examine your disk should you give it away, as you say you are planning to.

There are two things you can do, depending on your level of paranoia. You can get some software that will truly erase everything, overwriting every byte on the disk, or you can trash the disk.

I recently had the opportunity to try some software from Blancco. I simply popped the floppy disk into the machine, rebooted, answered some questions and it then sat there erasing everything. I did not try to recover anything afterwards, but the disk seemed quite 'blank'.

Blancco Data Cleaner is 24.95 euros (about HK$220) from

If, however, your level of paranoia is truly high - shall we say 'military grade' - then the best suggestion I have is to take the disk out and replace it with a new one.

This may not be quite so silly as it sounds. If you take the old one out, you can get a case for it, depending on its size, and attach it through Firewire, if your new machine supports it. You now have a back-up disk with all your data on it and a blank, new disk in the old computer you wish to give away.

You must ask yourself what the consequences would be if somebody were to read your disk. Have you got embarrassing personal correspondence on it? Perhaps you have confidential company data on the disk that may compromise your business.

Considering how cheap hard disks are today, you may be better off getting a new disk.

Questions to Tech Talk will not be answered personally. E-mail Danyll Wills at