The best way use any Linux Live Cd and format the drive. It will remove grub files even. If you want to create partitions again, you can use use utility named as CFDISK in linux itself which is better than any other tool. I will suggest you to use Ubuntu Linux Live CD which is freely avaiable and even can be shipped at your place free of cost. It contains a tool named as GPARTED. that is the best tool to handle partitions.