if adb is not working you still may have fastboot.
try powering kf off type "fastboot devices" into a command line. (open prompt in folder where you have fastboot installed on pc) it should say waiting for device.
then plugin kf to usb cable and power on if you've got fastboot it's easy, if you haven't it's a factory cable or a door wedge
Sent from my Galaxy Nexus using xda premium
Gnex: Dreams 4.4 KitKat
Kindle Fire: HashCodes CM11
Nexus 5: SlimKat
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