How to turn off the automatic update of the Amazon
1. Root Kindle Fire HD (Guide at: Guide on How to Root Kindle Fire HD 7, 8.9, Fire 2)
2. Open Root Explorer (Go to RW RO)
Access to: / system / etc / security / otacerts.zip edit the file name otacerts.zip otacerts.zip.bak
So the Kindle Fire HD you have not automatically update anymore. In case you like to update, you can download the latest firmware at the homepage of Amazon amazon.com, copied to the Updates folder of the Kindle Fire HD, on the Settings / Device / select Update to update to the firmware you want.
Preventing automatic OTA update of the Kindle Fire HD