Unfortunately, I believe you will need to factory fallback your device to allow yourself to start over. Since all of your books are backed up through your B&N Lifetime Library, your books will re-download once you've re-registered the device.
To complete a factory fallback:
1. Turn your device completely off.
2. Power up the device while holding in both the power button and the physical "n" button at the bottom of your NOOKcolor.
3. The device should begin to power up and you will see the welcome screen however keep holding both buttons down and the device will power down.
4. Repeat step 2.
5. When the welcome screen comes up, release both buttons.
6. The device will begin to power on and then a window will pop up asking if you would like to restore your device. Press the "n" button once and again to confirm.
7. The NOOKcolor will restore itself to full factory defaults and will startup as if it were brand new.
8. Re-register your device (while connected to a WiFi network) and you will start over fresh
just make sure you are plugged in or this won't work. i tried multiple times on battery and no luck. i plugged it in and worked the first time! PLUG IT IN!