format Formats a disk to accept Windows files ... TIP: You can resize a Partition even if Disk Management fails using DISKPART and FSUTIL command-line tools for Disk Management.

After formatting, DiskPart will automatically assign the letter to the new partition. However, you could manually do that using the assign letter=G command. Of course, replace G with the letter ...

To resolve the error, you have to clean your disk before using the format fs=ntfs command. The steps for this are as follows: Launch the Command Prompt as administrator. Type Diskpart and hit Enter.