The answer to your question of course depends on what you intend to do with the old computer, and just how sensitive the data on that HD really is.
If you're going to send it to the dump (landfill) then you had just as well use KillDisk or some such wiping program on it. Or even better, remove the hard drive and use it for target practice or sledge hammer practice.
Only if you literally beat it to death, can you be assured that no-one can ever reclaim anything off of it.
Then bury it in your back yard.
If you're just going to give it to a friend or to a student, deleting all your data off of it and doing a Defrag would be sufficient. The defrag will write good data over what you've deleted.
Let's just say that I had some data on a system that I wanted to give away to a student (for instance)
I'd delete everything off of the HD that I wanted GONE and remove my name, etc. in the registry.
Then I'd make a Ghost Image of what remained to a second HD or DVD. Then I'd use killdisk or Disk Eraser (from OnTrack) to clean the HD's surface. Then I'd re- FDISK and format the HD, setting up my partitions and verifying the disks surface to receive data. Then I'd restore my Ghost Image to the C: partition.
That would pretty much assure that no residual data remained.
This whole process would usually take less than an hour (or two) and I'd not have to worry about my old data ever falling into the 'wrong' hands. And I'd know that I have a nice clean and stable hard drive.
(Ghost, backs up only active files,,,,not deleted files. It backs up files exactly as you would see them in Windows Explorer.)
To prevent things from ever going into your Recycle bin, hold down your left Shift key when you click Delete from the context menu, while pointing to the file or folder to be deleted. That will permanently delete the file and it will NOT go into the Recycle Bin.
In another forum we had a gentleman who had worked for the CIA. We had this conversation and he told the poster, "sell your PC in a yard sale and let me get ahold of it and I'll RUIN YOUR DAY".
I don't think I have to tell you what he meant by that.
Even when you think you've totally deleted a file from your HD, there's a Ghost Image of it left there that some very sophisticated machinery can recover.
This problem will rear its ugly head again in reference to data disks that we make for backups.
To absolutely eliminate the possiblility of any of my data backup CD's from ever getting into the wrong hands, I went to "Staples Office Supply" Store and got me a CD Shredder. It's a Cross-Cut Shredder and makes tiny little pieces out of a CD or credit card. DATA GONE!
The day I brought it home, I shredded over a hundred old CD's. Boy, that was fun!
As for my old ZIP disks, I beat them to death with a Ball-Peen hammer. Then burned them!
Good Luck to ya,
Edited by The Shadow, 14 May 2006 - 01:14 PM.