Formatting large USB memory sticks using FAT16

FAT16 had a long run, from the old days of DOS up through to Windows 95. I thought the days of 2GB volumes were long gone. That is, up until a week ago when I lost all networking on an ESXi host. I needed to get the latest driver on my host and as the band Cinderella puts it, “you don’t know what you got till it’s gone.” Without networking, my best option was to load the drivers on a USB thumb drive.

Cinderella likely saved these lyrics to a FAT16 volume

In order to mount the thumb drive to an ESXi host, it has to be formatted using the FAT16 file system. Modern Windows can still format using FAT16, but it’s no longer possible from the GUI.

Enter Diskpart!

Diskpart has been around since Windows NT and thankfully it’s still a regularly maintained component of Windows. Because modern thumb drives far exceed the FAT16 file system limits, we have to partition the device so that it can be formatted with FAT16.

  1. Open a command prompt and enter diskpart (located in x:\Windows\System32)
  2. Type “list disk” and identify the thumb drive. In this example it’s disk 6
  3. Select the thumb drive by typing “select disk 6” (where 6 is the number identified in step 2) list-disk
  4. If the thumb drive has been previously formatted with a modern file system, we’ll need to delete all partitions. Enter “list part”
  5. As we only have one partition on this drive, enter “select part 1”
  6. Enter “delete part”delete-partition
  7. Create a 4GB partition by typing “create part primary size=4000”create-partition
  8. Type exit
  9. Format the disk for FAT16 by typing “format X:\ /FS:FAT/Q” in your command prompt where X: is the drive letter of your thumb driveformat
  10. Mount the thumb drive on your ESXi host and install your driversmount-USB





Matt Bradford


  1. Hey Matt, thanks for the info!

    Just as an FYI, I had to use the “clean” function in the diskpart tool to make sure the device was clean, before creating a new partition. This nuance may help others follow the instructions without any hiccups.

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