
In computing, diskpart is a command-line disk partitioning utility included in Windows 2000 and later Microsoft operating systems, replacing its predecessor, fdisk.
Run Command prompt and type:
C:/>diskpart
At the DISKPART prompt, type:
list disk
Make note of the disk number of the disk where you want to create a simple volume.
At the DISKPART prompt, type:
create volume simple [size=n] [disk=n]
At the DISKPART prompt, type:
assign letter=D