Can You Re-Register After Deregistering on Kindle?by Jane Williams
Registering your Kindle device to your Amazon account enables you to purchase and download books, magazines and other content directly through a Wi-Fi connection. You can deregister and then re-register your device to different Amazon accounts as often as you like.
Deregister Your Device
You can select the "Deregister" option under "Settings" on your device (for exact instructions for your particular Kindle version, see Resources), or deregister through your Amazon account by signing in to Amazon.com, selecting "Manage Your Kindle," selecting "Manage Your Devices," choosing your device, and then clicking "Deregister." Note that deregistering your Kindle wipes all books, apps and content you purchased with that account.
Register With New Account
You can re-register your Kindle through the device itself. Go to the "Settings" menu, select "Register," and then enter your Amazon account email address and password to connect your device to your account. If you do not have an Amazon account, you are prompted to create one.