HELP FILE

Q I bought a new computer, but I'm afraid to dispose of, sell or give away my old machine without making sure all of my data is gone first.

AAs this reader knows, deleting a file in Windows doesn't prevent somebody from recovering it later on. Fortunately, a pair of free, open-source programs can permanently scrub data off a PC.

To wipe out individual files, try Eraser ( http://heidi.ie/eraser). Once installed, it lets you right-click on a file and select "Erase"; the program will overwrite the file dozens of times to ensure that no traces remain. Eraser can also overwrite all of the free space on the hard drive with random data to obliterate any leftovers of deleted files.

If you need to scrub the entire hard drive -- and you have a CD to reinstall Windows from afterwards -- use Darik's Boot and Nuke ( http://dban.sourceforge.net). This download comes as a "disc image" file which you must burn onto a data CD. If your software doesn't recognize the file, try the free disc-burning utility at http://isorecorder.alexfeinman.com.

Once you've burned the Boot and Nuke CD, pop it into your computer and restart. When the PC flashes a message about which key to press to edit the boot order, press that key, then choose the drive holding the new CD.

When the text-only "boot:" prompt appears, type "autonuke" to wipe all the data off your drive. Then leave the computer alone -- it may need a few days to grind through this work.

For a less comprehensive disintegration of your data, type "quick" instead and you can be done in a couple of hours.

Got a Mac? To vaporize files, use the Finder's "Secure Empty Trash" command in Mac OS X 10.3 and 10.4. On older systems, try Next Wave Software's free Burn ( http://www.thenextwave.com). To blank the drive, start the computer off the system CD and run Drive Setup (Mac OS 9) or Disk Utility (Mac OS X) after selecting its "zero all data" option.

-- Rob Pegoraro

Rob Pegoraro attempts to untangle computing conundrums and errant electronics each week. Send questions to The Washington Post, 1150 15th St. NW, Washington, D.C. 20071 orrobp@washpost.com.