I just helped my dad upgrade to a new PC. We built it from components purchased from Newegg. So now he has an old computer, which although very slow, still works. He’d like to give it to a school or other charitable organization instead of it being trashed. But of course before doing so he’d like to erase all his personal data and return it back to a factory state. After using TurboTax and Quicken and automatic email logins, you don’t want personal info left behind. Here is how to do that:

1) locate your manufacturer’s CDs for reinstalling. Assuming you bought a complete PC from a manufacturer like Dell or similar, when you first got the computer it should have come with a number of CDs for reinstalling the hard drive. You did keep those, right? If not, contact the manufacturer and they should be able to send you replacements, probably for a cost. Less-old computers may have those CD images hidden on the hard disk, with a utility to burn these CDs at home.

The most important CD is to reinstall the operating system. There may be other CDs for utilities and drivers, but with most of that newer software can be downloaded. So find the operating system CD before you do anything else. If you use Windows, you’re not going to want to plunk down $100-$200 for a replacement copy of Windows, especially for an old PC that’s worth less than that.

2) download a copy of dban: Darik’s Boot-and-Nuke. You’ll get an iso file from the web site. Then you’ll need to burn that iso into a bootable CD. Make sure that when you do that burn, you create a CD from the iso image, not a CD that has the iso file in it. Most burning software will label this something like “Create a CD from an image”, and the file selection dialog for the image file will include “*.iso”.

3) make real sure you have copied everything you need from the old computer. Since new computers typically have a way bigger hard drive than the old ones, you may just want to share the C drive on the old computer, and copy the entire old drive to the new computer over the network. (Don’t copy it into the root of the new hard drive, instead copy it to someplace like c:\Documents and Settings\myuserid\My Documents\old drive.) Yeah, 90% of that is stuff you won’t need and can delete later, but it’s safer to lazily delete unneeded content rather than explicitly copy just the needed content. It may be best to wait a month or more before erasing the old disk with dban, to give yourself time to remember everything you need.

4) put the dban CD into the old computer and boot from it. It contains it’s own stripped-down operating system that will bring you to a menu. You can wipe the old computer’s hard drive using a technique that approaches what the government considers secure. Note that simply booting into Windows and deleting files using Windows Explorer does not really remove the file data from the hard disk, it just removes the file entry from the index. This is like removing an entry from a searchable catalog in a library, but leaving the book on the shelf. If you go wandering you can stumble into the book even though it’s not listed in the catalog. Dban wipes all the shelves multiple times. It may take a couple hours to run.

5) use the manufacturer’s reinstallation CD’s on the old computer, as if you just installed a replacement blank hard drive. Your hard drive is blank, really blank. There may be multiple CD’s you need to get the OS back up and running.

6) install a free anti-virus such as Microsoft Security Essentials

7) make sure Windows Update is enabled. Look in My Computer -> Properties -> Automatic Updates. Run an update check now by opening up Internet Explorer and going to http://update.microsoft.com. Install the ActiveX plugin and download all the critical updates. This may take a while, especially if a Service Pack is included in the updates.

8 ) put on new copies of the standard stuff. If you use Firefox, download the latest instead of using whatever ancient version is on the old manufacturer’s CD. Same thing for utilities, especially Adobe Acrobat.

9) when you give the old computer away, make sure you include all the manufacturer’s CDs, so the new recipient can upgrade the hard drive if they run out of space or if the disk crashes.

10) sleep well knowing that your old computer is helping someone instead of making a landfill larger.