Permanently removing data
Thinking about selling or giving away your computer? Or maybe you want to sell, give away, or dispose of a hard drive. First, you need to remove any personal or confidential information. Delete your personal files in folders like My Documents or anywhere else you stored files. Also, uninstall any programs that you enter personal information into. Create a new user account and delete the old one to remove information that is stored in your user account. Windows stores information from some programs here.
Just deleting the information isn't enough. The data stays on your hard drive until your computer needs to save something else to the same location. There are programs that can undelete these files. In order to permanently delete the data, you need to do a bit level overwrite. The free version of CCleaner allows you to do this. Select tools then drive wiper and select wipe free space only. Selecting 1 or 3 passes should be fine. 3 passes means that the data is overwritten 3 times. Check the boxes next to the drives you want to wipe. Finally, click wipe to permanently wipe the data that you deleted from your hard drive.
Another option, if you don't mind wiping everything on the hard drive, is to use DBAN. This is not as easy to do, but you'll know you didn't forget to remove something. You may want to have a friend that is good with computers help you because you will need to create a boot disc from an ISO file, change the bios settings to boot from a disc, and reinstall Windows. This article explains how to use DBAN. To burn an ISO file to a disc in Windows 7 or 8, just right click the file and click burn to disc. Make sure there is a blank disc in your cd/dvd drive. This article explains how to reinstall every version of Windows.