SImply use any disk partioning software program or you can start your computer and boot into DOS and run "F" which is a way to FORMAT it disk on that drive to wipe out all partions and anything else contained on it.
STart with a fresh no data disk.
On Hiren's ultimate boot cd is disk tools. One of them or several would also do this for you but you have to tellyour computer to boot to CD with that disk in the cd or dvd tray... It will boot directly to that.
Lots of really good stuff on that cd. Maybe you can google Hiren's and download it and make yourself that disk full of useful tools.
Hope this might help a little Zim..