In addition to the password you use for your Barnes & Noble online account, your Nook passcode restricts access to the device -- if you enable passcode protection, you'll have to input this four-digit code to unlock your Nook before use. In a high-tech world full of passwords and security questions, it's easy to forget a code or two. If your Nook passcode has slipped your mind, it only takes a little tinkering to reset it.
Enter your Nook passcode incorrectly three times. At this point, you'll be given to option to “Disable pass code using account credentials.” Select this option.
Enter the email address and password associated with your Barnes & Noble online account. This unlocks your Nook and disables your passcode, giving you the opportunity to reset it.
Tap “Settings” from your Nook's Home menu, then tap “Device” and “Enable Pass Code” if you're using a Nook 1st Edition. For Nook HD or HD+, tap “Settings | General | Security | Screen Lock,” then toggle the passcode switch on and select “Set Passcode.” If you're using a Nook Tablet or Nook Color, choose “Settings | Security | Device lock passcode | Enter Passcode.”
Enter a new four-digit passcode, enter it again to confirm it and then select “Submit” or “Continue” to finalize your new Nook passcode.