How to turn a EFI System Partition USB drive to FAT32

USB drives that are formatted as a EFI System Partition don’t work in Windows 7 and are unable to be managed using the Disk Management tool. This can leave you with a USB drive that cannot be completely used, for example a 16 GB drive with only a 2.5 GB partition that can’t be extended into the unallocated space.



The steps below show how to use the DISKPART command line tool to reformat the USB drive. You will need local administrator access on the computer to follow these steps. The process will involve wiping the USB drive – back up before progressing.


  1. On your keyboard, press the Windows button + R
  2. type DISKPART and click ‘OK’
  3. USBDriveNotFullCapacity2
  4. Click ‘Yes’ if prompted by the User Access Control
  5. DISKPART will open in a command prompt window
  6. Type list disk and hit enter
  7. USBDriveDiskPart2
  8. You will need to identify your USB drive by size, in this case I can see it is disk 2
  9. Type select disk 2 (where 2 is the number from the previous step)
  10. The command prompt will respond by saying “Disk 2 is now the selected disk”
  11. Now enter the following commands
  12.  attributes disk clear readonly
    convert mbr
    create partition primary
    select part 1
    format fs=fat32  quick
    assign letter (letter)
    list volume
  13. USBDriveDiskPart3
  14. Type exit and hit enter to close the window.
  15. You drive will now be reformatting using the full capacity as FAT32