The Windows disc will have a format option during the option. You can wipe it then. If you want to wipe it before even installing Windows, you can use Gparted or a live Linux CD, such as Ubuntu, to wipe it:
Gparted: http://sourceforge.net/projects/gparted/files/gparted-live-stable/
Xubuntu - I prefer this interface over Ubuntu - http://sourceforge.net/projects/gparted/files/gparted-live-stable/