1. Open a Command Prompt or PowerShell window and type DISKPART at the prompt 2. The first thing that you want to do is have DISKPART list the hard disks that it sees so that you can tell it which one you want to work with. DISKPART>list disk 3. Then look at the list and you will probably see a disk with a small partition (around 200mb) which should be the EFI partition. You will need to select the disk because all the commands are applied to the disk you selected. DISKPART>select disk 2 4. Now all you have to do is tell it to clean the disk. This will remove all the partitions on the selected disk. DISKPART>clean