If you want to give away a computer, it’s best to securely erase the hard drive first in order to prevent someone from recovering sensitive data from it after it leaves your hands.
The problem with this advice is the lack of a comfortable, familiar way to do it.
But I found one. It’s called Privazer.
I think Privazer makes some dubious claims. It’ll make my system faster? Really? Not usually, it won’t, and in those rare cases when deleting files would make a difference, any disk cleanup utility will provide the same benefit. But in spite of that particular dubious claim, the tool has its uses.
One very nice use, not mentioned on their web site at all, is preparing a PC to give away.
Just insert your Windows CD, instruct it to reformat your hard drive (a quick format is fine), and then when it finishes, install Privazer–as a portable app if you wish, and let it clean your free space.
If you just want to give away a hard drive, plug the hard drive into a working PC, delete all the files with Windows Explorer, install and run Privazer, and let it do the rest.
I do have two concerns about the program that keep me from recommending it unreservedly. One is that the page doesn’t go into detail about how it overwrites the data. Ideally, you want to overwrite the data about seven times. Once each with all 1s and all 0s (in binary), and with random data the rest of the time, is a reasonable approach. Overwriting the data once with all zeros will prevent most consumer-grade software from recovering the data, but won’t necessarily keep out a determined scavenger. All the page says outright is that it uses different methods for hard drives and SSDs, which strongly implies it’s doing multiple overwrites, but when it’s my client’s data, I need to know.
My second concern is what it does with slack space. Windows normally writes 4K blocks. So if you write a 7K file, 3K of that last 4K block is unused–and contains data from whatever file used to live there. Potentially there could be usable data sitting in that slack space, so a truly thorough wiping utility should inspect and clear slack space as well.
Not knowing how it handles the first problem and whether it addresses the second one at all are reasons why I’d say it’s good enough for personal use, but until or unless they answer those two questions, you have to assume it’s not good enough for corporate use.