Put the hdd in another PC or a dock. Right click on the start menu button, select Disk Management, scroll down on the bottom to find the hdd (make certain that it is the hdd you want to format, not the one containing Windows). I have deleted my boot partition by accident before. Right click on each partition and select delete volume. It should show the entire drive as Unallocated space. Right click on the hdd again, and select Format. Just click through using the default settings if you want a single NTFS partition. It should be ready to go.
Note: this will wipe all the data.
