How do you create a bootable partition on a USB drive?
Solution 1:
try using UNetbootin.
Solution 2:
I have followed this article to do exactly what you want: http://www.pcmag.com/article2/0,2817,2041234,00.asp
Solution 3:
I've had success using WinGrub on a machine that only had net access. (No bootable usb, broken cd drive.) The site has changed since then: https://gna.org/projects/grub4dos/. I don't have the details any more, but I was able to boot GParted off of a USB key on that old broken machine. You can also use it to boot ISO images. You may not even need WinGrub if you have GRUB on your machine already.