You never want it to happen, but your Windows Phone could get lost or even stolen. If that occurs, you can ring, lock, or even erase your phone to help you find it or protect the data on it. But you may also want to make sure someone can't easily reset and reuse it without your permission. That's where Reset Protection comes in.
Reset Protection is a free service on account.microsoft.com that provides an extra layer of protection so that if your phone ends up in the wrong hands, it can't be easily reset or reused. (Reset Protection is available only for some new phones running build 8.10.15127.138 or later.)
Turn on Reset Protection
When you set up your phone, sign in with your Microsoft account and accept the recommended settings. That's all you need to do to turn on Reset Protection. If you don't turn it on during setup, you can always go to Settings
After you turn on Reset Protection, you'll get a "Welcome to Reset Protection" confirmation sent to the email address associated with your Microsoft account.
To turn off Reset Protection before you sell or give away your phone
Before you hand off your phone, remove all of your personal info and turn off Reset Protection-the recipient won't be able to use the phone unless Reset Protection is turned off.
If you want to carry over things to your next phone, back up your stuff.
Select Settings> System > About > Reset your phone.
If you're ready to erase all of your personal content on your phone, select Yes, and then select Yes again to verify.
Type your Microsoft account password, and after a few moments Reset Protection will turn off.
To turn off Reset Protection when you no longer own the phone
If someone has received your phone and you didn't turn off Reset Protection, the recipient won't be able to set up the phone. Here's what you can do:
Next to the phone you no longer own, select Remove phone.
Select the I'm ready to remove my phone check box, note the recovery key, and then select Remove. The recovery key will display on the page and will also be emailed to you.
When you're certain that you have your recovery key saved, select the I've kept a copy of the recovery key check box, and then select Okay.
Forward the recovery key email to your phone recipient.
Your phone is no longer listed on account.microsoft.com/devices, and the recipient can remove Reset Protection during phone set up using the Disable using recovery key option.
Buying or getting someone else's phone?
Here are a few key points to consider when taking ownership of a previously owned phone:
You can check the Reset Protection status of the phone at account.microsoft.com/resetprotection. On the Reset Protection Status page, type the IMEI or MEID. Find it by dialing *#06# on the phone.
If the phone is set up but locked, contact the previous owner. That person should have the password you need to unlock it so you can set up the phone.
Of course, always know who you're getting the phone from.