Tried on Windows 8.
On this step
7) Soon, you’ll see your Kindle detected as a new device.
Your PC shouldn’t be able to find any driver, so let’s help it: point the driver path where you stored Kindle-Fastboot.inf and let the PC load the driver.
The driver failed to install, it says can't find the specific file. What file does it need other than the Kindle-Fastboot.inf? Does it want the libusb0.sys?