If you're recycling your computer, smartphone or tablet, there's one significant problem you may have ignored: If you don't wipe them clear of data, you could become a victim of identity theft. Merely deleting files using normal system tools won't really do the trick --- you need to do a much deeper cleaning. Here's how to do it.
(Note: This article is an update of a previous article that ran in December, 2007; while some of the older information still stands, a lot of other things have changed since then.)
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Cleaning up cell phones, smartphones and tablets
Smartphones and tablets essentially pack your entire life into a small package, including your contacts, emails, records of incoming and outgoing phone numbers, social media information...and more. So you want to make sure that someone else can't get access to all that information.
You could try deleting individual apps and contacts, but the odds of doing that effectively are close to zero. Instead, you want to do a complete reset of your phone to wipe out its data and restore it to its factory settings. How you do this varies from operating system to operating system, and sometimes even device to device. These are general instructions that should work with most devices; however, it's best to check with your manual or manufacturer just to make sure.
Android: For versions before Android 4.0, press the Menu key from the Home screen and select Settings/Privacy/Factory data reset. You'll get a warning screen. Scroll toward the bottom and tap "Reset phone." If you also have an SD card in the phone (and don't want to use the data in your next phone), also make sure to check the box next to "Erase SD card."
For Android 4.0 or later, go to Settings and look for "Backup and reset." Tap that, and then, on the next screen, tap "Factory data reset." You'll get a warning screen along with a list of all the accounts you are currently signed into.
iOS: Go to Settings/General/Reset and then tap "Erase all Content and Settings." (This is specifically for Version 5; the process may differ slightly for other versions.)
Windows Phone 7: Go to the Home screen, then tap the Application Menu Key and select Settings/ System/About/ and tap the "Reset your phone" button.
BlackBerry: Head to Options/Security options/General settings, and then tap menu. Then select Wipe Handheld.
Wiping computer hard drives
Deleting files, folders and applications -- and clearing the data from the Recycle Bin -- won't do the trick if you're going to recycle your computer. Anyone can easily recreate that data using commonly available tools. Even if you reformat your hard disk, if someone really puts their mind to it they can recreate the deleted data. This can be a serious problem.