How to Reset a Windows 10 device

1. Make sure you backup files that you want to save. 
2. Select Start​  > Settings  > Update & Security  > Backup  > Add a drive, and then choose an external drive.
3. After you've backed up the info you need, select Start​  > Settings  > Update and security  > Recovery.
   
   
   
4. Under Reset this PC, select Get started, and then follow the instructions on the screen. Resetting your device removes your files, settings, and apps, then re installs Windows.
    
   Remove a device from your Microsoft account

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   After you've backed up and reset your device, you should remove it from

    your Microsoft account.

    Here's how:

   1. Go to https://account.microsoft.com/devices, sign in, and find the device you want to remove.
   2. Select Show details to see info for that device.
   3. Under your device's name, select More actions > Remove.
   4. Review your device details, select the box for I'm ready to remove this device, then select Remove.

   You can then unlink the device from your Microsoft account so it doesn't affect your Microsoft Store device limit:

   1. Sign in with your Microsoft account at https://account.microsoft.com/devices.
   2. Find the device you want to remove and select Un-link.
   3. Review your device details and select Un-link.