Originally Posted by proximus
Ok, I made three screenshots to clarify the situation for you guys.
3) The MfgTool: well, I selected the USB port of the Kindle in the "Configuaration" menu and then I picked the choice "Kindle main" and then clicked "Start". I tried a few times, waited for a long time and nothing happened so I just closed. Is it supposed to be that lengthy?
Your screenshot indicates that you're not booting the kindle in USB downloader mode, so the MfgTool can't work. Not sure what the key combination is on the K4 to get it into usb downloader mode - look in the simple debricking thread or any related howtos.