Sometimes for some exceptionally unlucky individuals like yours truly, a bricked kindle fire may stop being accepted as valid USB device making windows show the “USB device not recognized” message, a message one may associate with bad USB flash drives. Unless you manage to get your kindle fire recognized again, there will be no ADB, no Kindle fire utility, and no unbricking tools for you.
In my case, and this worked a couple of times. Turning your kindle fire off while it is connected to USB by holding the power button for up to 20 seconds, then turning it back on while it is still connected solved the problem.
When the kindle fire starts, in will be recognized as a “Kindle” device without a valid driver, that’s your opening, don’t miss it. Know that if you disconnect & connect you will be back to the usb device not recognized message.
Once you have the kindle device, right click it and install a driver manually for it. if you don’t have the driver, you can find it with any kindle fire utility.
Note that this may not work on a first try, you may want to try it on a different computer, if you can’t get the kindle fire to recognize. a 32bit windows XP maybe is your best bet.
Wish this was helpful, I know how frustrating a bricked kindle fire can be. Good luck!