Another option, however, is to download a CD image of any of the many free Linux distributions and use that to erase and reformat the drive. Once Linux is installed, you'll be selling a fully-operational PC that's stuffed with lots of useful applications software -- and as a bonus, you won't have to worry about unintentionally violating any of Microsoft's Windows license terms.

But neither of these methods may be sufficient for truly sensitive data. You may want to invest in a software utility that can on old drives, making them unreadable even by data-recovery services.

The important thing to remember is that even if your day-to-day activities don't seem as sensitive as those of a political campaign, even a small business will have secrets worth protecting. Customer names and addresses, company credit card information, billing rates, internal memos and e-mails, and employee lists could all have value to a competitor. Make sure you've cleaned up the drives and flash memory of your old PCs, laptops, and handhelds thoroughly before you put them up for sale.

Has your company ever unwittingly given away confidential information in this way? Are you sure? And what steps are you taking to prevent it happening in future? Sound off in the PC World community forums.

is a freelance technology writer based in San Francisco.