When you're recycling your old laptop or desktop, the simplest and most secure solution is to physically remove the hard drive. You can then install the old drive in your new computer, or put it in a USB hard drive enclosure and use it for backup or portable storage. But if screwdrivers intimidate you or you want the computer to remain functional so someone else can use it, you’ll have to invest a lot more time.



To make sure your personal data isn't recoverable by reasonable means, do a secure wipe: This not only deletes your data but also overwrites the data a certain number of times, which makes the data much more difficult to retrieve. Unless you're worried about corporate espionage or government intervention, three passes is generally sufficient. After that, some of your data may still be retrievable, but it would take a significant amount of time and expertise to do so.

You can securely erase a Mac or PC by making a free bootable DBAN CD or flash drive. When you boot your computer with DBAN, you can choose various levels of secure erasing and select which drives you want to erase, if the computer has more than one. Or you can type "autonuke" to securely erase all drives. (For PCs, you can also use secure file erasers such as File Shredder, Eraser, and Freeraser to erase individual files and folders instead of the whole drive.) You can also securely erase a Mac using its built-in Disk Utility. First boot to Recovery mode by holding down the Command and R keys while turning it on. Once booted, select Disk Utility from the menu, and then Continue. Select your hard drive, then select Security Options. From here, slide the slider to Most Secure. Follow the prompts asking if you really want to erase the drive, and sit back while it runs.



Note that DBAN works only on standard hard drives. If you have an SSD you’ll have to try another program. SSD’s are more complicated to erase than standard hard drives. Check with the SSD manufacturer to see if they offer a free utility you can use. If not, then try Parted Magic. As with DBAN, you’ll need to make a bootable CD or flash drive, then boot to it and follow the instructions. Parted Magic can be downloaded with options starting at $9.

DBAN and Parted Magic are good choices as long as you don't want to repurpose the PC with the OS intact. If you're on Windows 8, though, you can do a factory reset with Windows reinstalled, with an option to do a secure erase in the process.



Securely erasing a standard hard drive can take several hours or even days to complete, depending on the size of your drives, so don't do this the night before donating or selling your device. Because SSDs are faster than hard drives and they store file data differently, a secure erase takes only seconds to minutes to complete.



You can also this method to erase external portable hard drives securely. Just take care to erase the correct drive and not a drive with data or an operating system that you want to keep.