SistemError asked the Desktops forum how best to prepare two aging PCs for their new owners.
The new owners probably want fresh installs of the operating system that the PCs originally shipped with (which I'm assuming is some version of Windows). And you definitely want the computers to leave your home without any comprising information, like bank account numbers, still on them.
That means you must first securely wipe away sensitive information. Then you should reinstall the operating system to its factory condition.
A quick word about wiping: Deleting a file and emptying the Recycle Bin doesn't actually remove the file's data. "Empty" space on a hard drive actually contains remnants of deleted files that don't go away until new files overwrite them. Thus, you can securely wipe--or shred--all or part of a drive by writing data over it.
Most shredding programs offer several ways to do this, from simple one-pass wipes to extremely paranoid variations that take days to write over your drive 35 times. A single pass will render the data irretrievable to anyone without access to some very fancy, expensive hardware. So unless you think spies or the police are after you, that's sufficient.
But how you shred your drive could affect your ability to restore Windows. For some years now, most computers have come with a recovery partition required for restoration. If you wipe your entire hard drive with something like Darik's Boot and Nuke (DBAN), it will destroy that partition and make restoring Windows impossible.
Here's a better method: Delete all of the files that may contain sensitive information, then empty the Recycle Bin. Then you can use CCleaner Portable to wipe your drive's free space (you can use the regular version too, but if you don't already have it installed, the portable one is easier). Load the program, click Tools in the left panel, then Drive Wiper. Everything should be obvious from there.
Once the wipe is finished, boot into your recovery tool. If you don't know how to do that, check your PC's manual. If the tool gives you options for keeping or destroying data, go with the most destructive option--the one that doesn't save your data.
Read the original forum discussion.
Contributing Editor Lincoln Spector writes about technology and cinema. Email your tech questions to him at firstname.lastname@example.org, or post them to a community of helpful folks on the PCW Answer Line forum. Follow Lincoln on Twitter.