Fastboot not working for Kindle Fire HD
After some digging, I found a solution that worked for me. I hope this helps you too:

http://forum.xda-developers.com/showthread.php?t=2271909&amp;page=9


In Windows Device Manager, find Tate-PVT-08 in on the list.
Right click, and select Update Driver
Select Browse computer for driver software
Select Choose from a list of device drivers installed on my computer
Find Kindle on the list
Accept ADB composite interface