There is an increasing trend for people to upgrade their computer these days and this introduces two issues; how to transfer their data from the old machine to the new and then how to get rid of the old computer.
Getting rid of an old computer is simple... you can just take it to the tip or you may want to pass it on or even let it go to some third world country but all these options raise the issues of the data on the disk drive.
Whatever you're going to do with the computer, you really want to clear all your personal data from the disk.
Maybe you don't think it's all that critical because you never used your credit card on the machine, never bought anything online, never used online banking, etc. but you probably DID access email and use other things which required passwords... and then there's all those documents that could help an unscrupulous person perform identity theft and get enough information about you to gain access to all manner of facilities!
OK, that's the problem but how do you solve it?
You probably know that simply deleting files doesn't get rid of them (even if you empty the recycle bin). They're still there on the disk and if you've ever made use of my service to recover data from a failed disk drive you'll realise just how much data CAN be recovered. You really need to overwrite the data totally to erradicate all trace of their contents.
Fortunately this isn't a difficult task and can be done using a product such a 'KillDisk'. With these products you boot your computer from a CD and the program then writes all over the disk drive, thus obliterating all files totally. Alternatively it can be told just to wipe the unused data area, leaving any existing data intact, so you can delete all the data you want removing and then run the program in that mode.
Just remember that if you do a total wipe of the disk, the computer won't start because it'll have no operating system on it. If you want to pass your computer on to, say a deserving relative, then this is NOT the way to go!