Format c:\ nor fdisk doesn't erase the data on the hard disk, they only erase the addresses to them. I'm just pondering upon a way to completely erase the hard disk and still render the disk operable. I'm not actually going to but I would think it would be useful if you sell a hard disk and don't want anyone to look at your old files.
More aboutcompletely erase hard disk
Run a Low Level Format utility multiple times. The program is usually provided by the manufacture of the hard drive. That should be sufficient.
<font color=red>People and hard drives are like bandwagon fans and sports!</font color=red>