How can I restore my Kindle Fire HD after I deregistered it by mistake

1. From your computer: Visit Manage Your Content and Devices. Select Your Devices. Select your device or app and select Deregister in the Actions column. ...
2. From your device: From Home, tap the Menu icon, and then tap Settings. Tap Registration. In the Deregister Your Kindle dialog box, tap Deregister.

How to Register Your Kindle Paperwhite

Log in and click on "Your Account" and under Kindle Help click on Kindle Help Home.


Next click on Manage Your Content and Devices to the far right



Next click on Your Devices and it will show all your registered computers and devices


Select the device by clicking on it and you will get the opportunity to either edit it or deregister it.

You'll find instructions here: http://www.wikihow.com/Deregister-Your-Kindle-Fire-HD-Account

Log on to your amazon account. Then upper right of page click to open options on "Your Account". Then on the left side pane go down and click on "Manage Your Devices". When the device pages opens, see "Deregister" on the far right of your listed device. Hopes this helps.

I have seen this when the Amazon Certificates become corrupt. The only way to restore them is by doing a Factory Reset.
1. Pull down the upper Status Bar, select More+
2. Select the Device Tab
3. At the bottom you will see "Reset to Factory Defaults"
4. Answer Yes to reset everything

When this is done the Kindle will be back to it's Factory State, Deregistered, without data.

You would like to deregister the Kindle correct?
1. Make sure the Kindle is connected to Wireless
2. Pull down the upper status bar, select More +
3. Next select My Account
4. Find and click on "Deregister"

If I understand you correctly, you have a new Kindle Fire HD and would like to transfer the data from your old Kindle Fire to your new Kindle Fire HD. This is easy, follow these steps:
Step 1: Connect the old Kindle to Wireless. Pull down the upper status bar, select More + and then select My Account on the old Kindle
Step 2: Using the Old Kindle, select Deregister under My Account, let the task complete
Step 3: When the old Kindle has Deregistered, then pickup the new Kindle. If you accidentally registered this Kindle Deregister it and then Factory Reset the device.
Step 4: Now the old Kindle is Deregistered and the new Kindle is factory Fresh, let's begin the process.
Step 5: On the new Kindle, let's reboot after Factory Resetting the device. When the device powers back up you should be presented with a login Window. Go ahead and register the device to the same account as the Old Kindle. The sync process should begin automaticlly, it can take up to one full day to sync all your content.

To Deregister the Tablet
Step 1: Pull down the upper status bar, choose More +
Step 2: Choose Account - Deregister

I have changed the account on the fire hd many times when My Grandma let my mom borrow it. Just go to your Kindle and swipe down the tool bar. Then click "More" and then "My account" and then "De register". You should be able to then register a new user.

Tap the gear icon at the top of the screen. Tap "More...". Tap "My Account". Tap the "Deregister" button.