Also, remember that you only need to use this method if either you don't have a usb (very unlikely ), or your box image has become corrupt, as well as the bootloader.
In 99.9999% of the time, you will be able to flash using the usb cable. There will only be rare occurences when the usb booting will not work. Also, if usb booting doesn't work, then it's worth trying to remove all other usb devices (and maybe even all other cables to the box), just leaving the front usb port connected...