How to burn a Windows .iso to a USB device?

UNetbootin should work: http://unetbootin.sourceforge.net/

Or you could try a bit-by-bit copy:

1. Insert the USB device and then open Disk Utility (in 10.10 and older, System -> Administration -> Disk Utility).
2. Select the USB device from the list in the left of the program and detect where it was mounted: /dev/sd[1 letter][optionally 1 number]. For example, /dev/sdc or /dev/sdc1.

3. Make sure the USB device is unmounted (not safely removed, but unmounted) If it is mounted you can unmount it:

   sudo umount /dev/sd[1 letter][optionally 1 number]
   

4. Assuming the .iso file is in your home folder, open the terminal and write:

   sudo dd bs=4M if=[ur .iso] of=/dev/sd[that 1 letter]
   

   Example:

   sudo dd bs=4M if=windows7.iso of=/dev/sdc
   

And wait for it to finish. (The "bs=4M" - bit is optional, just makes it faster.)

1. Insert the USB device, then run gparted.

2. Select the USB device from the list near the upper-right corner of the GParted window and detect where it was mounted: /dev/sd[1 letter] (mine was /dev/sdc).

3. Make sure the USB device is unmounted (right-click and select unmount).
4. sudo dd if=[PATH TO YOUR .iso FILE] of=/dev/sd[THAT 1 LETTER]

   In my case: sudo dd if=/home/downloads/windows7.iso of=/dev/sdc

You must run dd as su or sudo. It's worth mentioning that gparted requires su as well, but will typically use gksudo to prompt for the password.

This means you can lock gparted to the launcher on a persistent liveboot USB for field diagnostics.

If you boot with UEFI (not BIOS or UEFI with BIOS compatibility mode (a.k.a. CSM)) all you'll need is GParted and a file manager.

The ISO must be configured for UEFI boot for this to work. I've successfully done this with both Windows 8.1 and Ubuntu 14.04, but I can't vouch for any other OS. (Edit: I just tried this with Windows 10 without success. Don't know why, but WinUSB worked so I didn't investigate further.)

This is what I do to create a bootable USB drive for UEFI firmware:

1. Create a GPT partition table on your USB drive. In GParted, chose "Device" and then "Create partition table...". Choose gpt in the dropdown.
2. Format a partition on the USB drive to FAT32 using GParted. All UEFI compliant firmwares must support FAT12, FAT16 and FAT32, so any of these should be fine, but NTFS will not work.
3. Mount the USB drive like you would any other external storage so you can access the filesystem on the partition you created.
4. Mount the ISO you wish to add to the USB drive so you can access the files in there.
5. Now, when you have access to both the ISO and the USB drive as filesystems in your file manager (Nautilus or whatever) just copy and paste all files in the ISO to the USB drive.
6. Add the 'boot' flag to the partition you've created and added the files to. In GParted, right click the partition, choose "manage flags" and then check the "boot" option.

(While testing this I couldn't mount the USB drive anymore after setting the boot flag. I don't know why, but GParted could still see it and the end result was still a bootable USB drive, so I guess it doesn't really matter.)

7. Restart your computer and choose to boot from the USB drive.

Once again: Please note that for this to work, your computer's firmware must be UEFI compliant and the ISO must be ready for UEFI boot.

If you find an EFI directory in the ISO that's usually a good sign.

To see whether you're currently using UEFI boot, run sudo efibootmgr -v in a terminal. If it lists a number of boot options you're good to go. If you're using BIOS compatibility mode you'll see something like this:

Fatal: Couldn't open either sysfs or procfs directories for accessing EFI variables.
Try 'modprobe efivars' as root.

For more information on UEFI, please read this excellent essay on the subject: https://www.happyassassin.net/2014/01/25/uefi-boot-how-does-that-actually-work-then/

Also, I don't think Ubuntu will work with Secure Boot enabled, so you'll have to disable that to be able to use UEFI boot with Ubuntu.