What is the best method of removing graphics card drivers?

[EdwardTeach]

I have just received my 670 oc (thanks ocuk!).

I currently have a 5850.

What do I need to do to cleanly remove the ATI drivers, before I put my nvidia card in?

 

[EdwardTeach]

Strong magnet swiped directly over the drive.

I tried your method because I didn't want to faff around with uninstalling drivers, and happened to have a strong magnet to hand. Something seems to have gone wrong though, my computer makes a beeping sound when I turn it on and the fans sound like they are spinning really fast. Any ideas what is wrong? Should I magnet the computer again?