Render an old hard drive's files unreadable the easy way.

This article appears in the May 07 issue of PC Advisor, available now in all good newsagents.

Data thieves don't have to be programming wizards to get their hands on your personal information. They often find hard drives containing sensitive data at jumble sales, car boots, charity shops, the council tip and even on eBay – netting them a real bargain.

Reformatting a drive or deleting its partition doesn't completely remove its files. Which is great, if you haven't kept up to date with backups – not so great if you're getting rid of an old PC. While putting files in the Recycle Bin makes them unreadable to Windows, it's no good if you forget to empty it. And if you did, the files are still recoverable with special software.

I destroy my old data using a block-erasure utility such as DBAN. This clever application overwrites each block on a computer's hard drive several times.

DBAN can create either a bootable floppy disk or an ISO file that you burn to a CD. Once you boot up from the startup disk – you may have to tweak your startup settings to boot from the floppy or CD – just a few keystrokes will begin destroying your data.

The Secure Erase Utility uses the Disk Drive Secure Erase command built into every modern hard drive's firmware. The wipe is incredibly fast and it can do the whole job in half the time of a block-erasure utility.

Get hammered

Commercial shredding companies use huge grinders to shred discarded drives into tiny bits. And security-minded consumers who want to be certain that their old disks are unusable have been known to chop them in half with an axe or drive nails through them.

A (marginally) less extreme approach is to give the outdated hard drive a few whacks with a sledgehammer. We recommend you wear safety glasses and that you warn any neighbours within earshot that you're about to embark on a stress-relieving bout of violence.

Encrypt and delete

Encrypting files on your hard drive prevents unauthorised access to your information, but you can use the technology to ensure that the files you delete aren't recoverable.

If you encrypt a file before you delete it then a file-recovery utility may be able to restore the encrypted version of the file, but the utility won't be able to decrypt it.

To use XP Pro's built-in encryption, right-click the files or folders you want to encrypt, choose Properties, Advanced, tick Encrypt contents to secure data, then click ok. You can encrypt any files except system files. Select all the folders on the C drive – except the Windows folder – and everything inside will be encrypted. Any files you later place in the folders will be encrypted automatically.

XP automatically creates a unique encryption key if you use this feature. But if you damage your installation of Windows without backing up the keys, it will be impossible to decrypt those files. If you choose to encrypt your files this way, you needn't run a secure erase tool to ensure your privacy: just delete the partition and format the drive.