How to restore factory Hard Drive / Flash drive Capacity

Problem description : Some external hard disks / USB flash drives do not show actual space as mentioned in the factory settings.

This is a common problem when you use an 8 GB USB drive to make it bootable to install a firmware/ driver on a server, which is a DOS flavored utility. After this, connect the flash drive to a laptop and it shows less than 2 GB. The reason for this is when making the flash disk to run a DOS program, it will format the flash disk with FAT file system. To correct this we need command line mode.

In Disk Management we can see the remaining space is available as unallocated. To partition it and make use of it, run the following from the command prompt:

Before executing the disk part command, make sure that the data from the flash drive is backed up as the command wipes data from the flash drive - or any other drive you select.

Run command prompt as administrator
Type "diskpart"

Type "list disk" it will show the following output (as example)

Disk ###  Status      Size     Free     Dyn  Gpt
                      --------  ----------  -------  -------  ---  ---
                      Disk 0    Online      2040 GB     0 B
                      Disk 1    Online       683 GB      0 B

Select all Open in new window

To select Disk 0:
Type "select disk 0" (or whatever number that corresponds to your flash drive or disk), and proceed at your own risk, in particular if you have other external hard disks or USB flash drives connected to your computer.

This will shows the output as "Disk 0 is now the selected disk."

In the prompt type "clean" if you are satisfied that you have selected the right disk.
Now the entire disk shows as unallocated. You can create new partition using disk management or by using the following commands

create partition primary
                      select partition 1
                      active
                      format fs=fat32
                      assign
                      exit

Select all Open in new window

After creating the primary partition and making it active, you can format the USB drive with NTFS file system from the windows explorer as well. Now it will show the entire space.