In GNU/Linux, you can create a bootable USB flash drive using an ISO disc image of another distribution, by using the command-line. The command that is used to create that is called ‘dd’.
By default, almost all USB flash drives use a common partition layout (which of course can be changed) that consists of a single, primary partition occupying the whole space. However, when you use ‘dd’ on an USB flash drive, it will destroy this layout and will create a new partition layout.
It will create a partition that is big enough to hold the data of that ISO file, followed by another special partition called ‘EFI System Partition’ that stores files related to booting etc and finally, the remaining space (if any) of the USB flash drive will be hold in, as an ‘Unallocated area’.
The thing is, other operating systems like Windows 8 will only recognize the ‘EFI System Partition’ (which is usually around 2-3MB) and the rest of the ‘free space’ will be unusable!. Even other advanced tools like the ‘disk manager’ in Windows, though it properly recognizes the partition layout, won’t let you create a partition on the remaining ‘free space’ and use that space either.
Not only in Windows, but some tools in GNU/Linux have also failed while letting me create a partition on this ‘unallocated area’ as well.
I personally don’t like this approach used by ‘dd’ (though it might have some advantageous), as it creates unnecessary complications, because you can still create a bootable USB flash drive, without having to repartition it this way, thus you will be able use it as usual (reformat, delete or add files etc).
Nevertheless, if you did not know this at the time you used ‘dd’ and looking for a way to get rid of it using Windows 8, then please follow the below steps. Not only by ‘dd’, you can use these instructions for getting rid of ‘EFI’ partitions created by other tools too.
Note: Before proceeding, please be aware that, this will destroy all the data on the drive!.
Press the ‘Windows key’ on your Keyboard and then simply type the below command.
Then Windows 8 will locate the ‘cmd’ application. Now, as shown below, right click on its icon and then from the options that will be listed at the bottom of the screen, select ‘Run as Administrator’.
When asked, click ‘Yes’ to the next message.
This will open ‘cmd’ with administrative privileges. Once it is opened, type the below command on its window (make sure the USB drive is attached).
Then wait for few seconds, until the command prompt changes into ‘DISKPART>’.
Now enter the below command.
This command, as shown below, will give you a list of all the disk drives that are currently attached to your computer (USB, IDE, SATA etc).
Now have a careful look at its output and make a note of the disk drive number of the USB flash disk that we need to restore to its original partition layout (in this instance it is ‘Disk 1’).
Once you know the disk number, simply replace the ‘Disk 1’ (unlike GNU/Linux, Windows is not case-sensitive, so you should be able to use ‘disk 1’ as well) part of the below command with your disk’s given name and execute it.
select Disk 1
When you issue this command, it will give you an output saying that, that particular disk is now selected (shown below).
Now to delete the partition layout of this disk, enter the below command (this will erase the entire disk!, so make sure the entered disk name is correct!).
If you get an error saying that somehow ‘diskpart’ was unable to do it (it happens sometimes), then try the ‘clean’ command again. If everything goes accordingly, then you should see the message ‘DiskPart’ succeed in cleaning the disk’.
Now all we have to do is to create the standard partition layout that is used in USB flash drives (a single, primary partition, occupying the whole space). For that, enter the below command.
create partition primary
If it was successfully created, you should see a message saying ‘DiskPart succeeded in creating the specified partition’.
Now open ‘My Computer’, double click on the USB flash drive’s icon, and Windows 8 will ask whether you’d like to format the drive or not.
Then make your selections from the ‘format disk’ window that you get next (when unsure, use the default settings), once done, click on the ‘Format’ button.
That’s it, now you should have restored your USB flash drive to its original partition layout and can start using it as usual. Good luck.
Credits: Some information via ‘Winability.com’.