A Mac enthusiast from Japan asked about deleting unwanted files recently. A few more questions have come in about deleting files and even shredding them in OS X. The Mac user's file in question was an aborted download - the system crashed during the download and left a partially downloaded file on the desktop. The operating system thought it was 'in use' and would not delete it. It may well be worth getting the software called SafeShred. Not only will SafeShred kill off the file, it shreds it as well. What this means is that even sophisticated data-rescue software should be unable to recover the file. SafeShred can be downloaded for free and then upgraded to a more powerful version, of which there are two: Pro and Xtreme. For basic shredding, the free version is adequate. It will shred the file with an overwrite bit pattern three times. Usually, that should be enough. However, if you have documents you believe are extremely sensitive to your company or your personal life and need to delete them, you may want to opt for the Pro or Xtreme versions of the software. Upgrading to the Pro version will cost US$15 and the Extreme version costs US$25. Both the Pro and Xtreme versions support the United States Department of Defence shredding standard. The Xtreme version will shred free disk space and entire volumes. It will also mangle file names, just to be safe. What this is all about, of course, is the level of paranoia one is willing to live with. As one would expect, the military is the most paranoid of all organisations and has precise guidelines on how to shred electronic documents. For most mere mortals, it may not be necessary to go that far. Nevertheless, if you have information that is worth millions, you may not want to be too cavalier about deleting it. A good time to shred files or a hard disk is when your computer is being sold. You may not want people prying into what you once had on your hard disk. If all you do is use an operating system command to delete data, much of it can be recovered. One word of caution about all this: what you do as a private individual is one thing, but what you do as a public company is quite something else. Enron executives got into a lot of trouble because they used electronic shredding to delete many documents. A public company's management cannot simply shred whatever it feels like shredding. If you have any doubts about whether your document is safe to shred, consult a lawyer. SafeShred can be obtained from the following Web site: http://www.codetek.com/php/safeshred.php Questions to Tech Talk will not be answered personally. E-mail Danyll Wills at techtalk@scmp.com .