Eventually, we all have a spare or old computer we no longer need that is sitting around collecting dust. Some of us might get the idea to sell it but others may decide to give it to charity. Whatever the reason is, you must make sure you properly delete the data on the computer you are donating off of the hard disk.
It is a common misconception that reformatting a drive deletes the data on your hard drive. Actually, when you reformat a drive, you really just the the drive to forget where the data is. The drive in your computer may not show anything there but it is still there until it is written over by saving new data. With proper tools, data from a formatted drive can be recovered quite easily.
DBAN or Derik’s Boot and Nuke is a free utility that will really wipe all data from your drive. Instead of reformatting a drive, DBAN actually writes 0’s or blobs of data over your data. DBAN has a variety of options to overwrite data over and over multiple times for when you want to be really secure.
To find DBAN, do a Google search for "DBAN." Once there, read the instructions on how to create a bootable CD and run DBAN.
!!!Warning!!! If you use DBAN on your C drive, you will erase everything and never be able to recover anything again. This is exactly what you want to do if selling or giving away a computer.